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Header data

May29th
2010 Leave a Comment Written by admin

Header data

Getting all the header data of browser by using Request object ServerVariable in ASP

When ever browser send request for a page to the server, along with the URL some more information also the browser provides to the server. This additional header information can be collected at the server end. Same way while sending back the content of the page requested by the browser the server sends some more header information back to it. All these header information can be collected at different ends and used in our scripts. We can access these HTTP header information’s and accordingly modify the content at server end. For example we need to display a different pages for different languages. By reading the header information on HTTP_USER_AGENT we can find out what is the language setting of the client browser and then redirect to that particular language page of the user.

To get the http headers we will be using ServerVariables collection of Request object in ASP. To display the value of a particular header we have to use the header name like this .

The above line will display the client browser details, with language settings etc. Here is one sample output for Firefox browser at client side.

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.8) Gecko/20061025 Firefox/1.5.0.8

We can display all the header information in one go without calling one by one by using its name. Here we have to use ALL_RAW

If we need formatted output with the list of headers (name ) then we have to use ALL_HTTP

We can display all the name value pairs for all the header information like this

Dim var
For Each var in Request.ServerVariables
Response.Write “<B>” & var & “</B>:”
Response.Write Request.ServerVariables(var)
Response.Write “<br>”
Next

The above code will display all header names and its values one by one.

How to get IP address of the visitor browser in ASP

We can collect IP address of the visitor by using Request object and its ServerVariable pairs. IP address of the user is required in many applications for different purposes. IP address are collected and logged for security purposes on different occasions like credit card process, member signup time etc. From the IP address we can identify the location of the visitor. However we will restrict ourselves only to know how to collect IP address of the visitor browser from the HTTP header information.

Getting the page referrer from header information in ASP

Visitors come to different pages of a site or move from one site to other by clicking links. When they arrive at a page, we can collect the URL of the referrer page ( the page which has send them here ) by using the Request object and its ServerVariable pairs.

By using referrer once we can know how many visitors are coming from google or from other search engines and what are the keywords they are using.

In PHP we can get the referrer URL and details are here.

In ASP we will collect the http header information to get the referrer. Note that if some one has typed the page name in address bar and reached the page then referrer information will not be there. Referrer information along with some other data are used for logging or tracking the visitors.

We will use http header name HTTP_REFERER to get the URL ( site address ) of the referrer . Here is the code.

<%= Request.ServerVariables(“HTTP_REFERER”)%>

Some browsers have settings to manage the header information. This way one of the important header referrer header information can be blocked. For Firefox browser at the address bar type about:config and browse through the settings, select and change the values if you want. ( be warned to change the settings , and read all the guidelines and read in details from Mozilla and other resources )

network.http.sendRefererHeader

The above header is to be made to 2 if referrer is to be send through header

Session Variable

May29th
2010 Leave a Comment Written by admin

Session Variable

Session ID and Object in ASP

Session object in ASP are there to store user specific information. In most cases sessions are used to maintain state as the user navigates through different pages. Some data we can pass by using query string, web forms and cookies but session variables has distinctive role than other ways while carrying data to different pages.

Say we want to carry the member login status to different pages and with this information the member can enter to members only pages. Here the session variables are stored at server side ( not at client side ) and it is connected to user browser. As long as the browser window is in contact with server, session details will be available and if there is no interaction from user end within a specific time the sessions variables will be destroyed. The user also can end or abandon the session. Let us learn some details about session object here.

Session ID
Session ID is the unique link between browser and the server. Once the session is created a session ID is generated which is a unique number and it is kept at user end ( client browser ) using cookies. Server keeps all the variables corresponding to this session ID at server side. Each time browser moves to different pages it submit session ID to server and server after matching returns all the session variables associated with this session ID. This session ID is also used in many cases to identify and keep track of user activity. For example in a shopping cart script we can keep all the purchases done by the visitor in a temporary table with a unique field storing the session ID. Based on this session ID what are the purchases and the total quantity, packets etc can be calculated at the checkout time. Session ID is the best way to maintain unique link with the server as many other visitors will be using the same site and doing purchasing at the same time. Here Session ID acts like the visitors unique shopping cart. Here is an example on how to get browser session ID

Response.Write Session.SessionID

When we should not use Session.
Sessions are used to store user specific information so it should not be used to store global information. For example there is an announcement for all the members that site member area will not be available during a particular period due to schedule maintenance. This message is for all so we should not use session to store this message. In another case we are using a membership system where user login id is to be available inside other pages, here details are user specific so they are to be stored using session

Load on Server
All session variables are stored at server end. So each session of the visitor adds load to the server resources as server has to maintain the session variables. Say for example we are using ten variables for each session of the visitor. Now at a moment if one thousand visitors logs in to the server then total session variables will be 10 x 1000. Imagine if the site became more popular and with growing visitor load on server also will go up. So only user specific requirements are to be kept in session and special care is to be taken up for high traffic sites.

Security
This is the biggest advantage of using session. As the data reside at server side so it remains secure irrespective of user browser environment. Some cases like user authentication results, passwords etc are kept in sessions only as users are expected to use different computers at different locations so they can’t be left at client side. Query string data gets easily exposed by checking the history of the browser.

Amount of Data
Better not to load the server with more session data as it drains the server resources. This is important particularly for high traffic sites. Now temporary tables are available in databases which are fast and maintain overall small size for database.

We will learn more on session start, session variable and session time out.

Creating Session arrasy and variables in ASP

At any time we can create a session variable and store data in it. Let us try to store user name in our session variable. We have given the name of our session variable as name only. Here is the example

session(“name”)=name

Note that the variable name has the name of the user and now it is available as a session variable. Let us learn how to display this session variable.

Response.Write “Welcome ” & session(“name”)

Above line will display a welcome message with the user name. Now let us try to display how many session variables are present for the user or the total number of session variables present for the user.

Response.Write Session.Contents.Count

The above line will display a number as total number of session variables present in our user session.

Removing all values from Session Variables
We can destroy or remove all session variables like this .

Session.Abandon

OR

Session.Contents.RemoveAll()

Selectively removing session values
There may be a requirement of selectively removing some session variables. Let us learn that . Here is an example of removing one particular session variable.

Session.Contents.Remove(“name”)


ASP Session array
We can store array in our session and carry that to different pages in ASP. We will learn how to assign a session array from a local array. Display all elements from a session array and how to assign a local array from session array.

Let us take the example of a simple array and assign some elements to it.

Dim language(3)
language(0)=”ASP”
language(1)=”PHP”
language(2)=”JavaScript”
language(3)=”Perl”

For our learning let us display all elements of the array once.

Dim i
For i = LBound(language) to UBound(language)
Response.Write language(i) & “<br>”
Next

Same way we will be displaying our session arrays also so a better understanding from the beginning will help. Now Let us assign our session variable to this array.

Session(“my_languages”)=language


Now we have our array in our session variable. Let us try to display elements of the session array.

For i = LBound(session(“my_languages”)) to UBound(session(“my_languages”))
Response.Write session(“my_languages”)(i) & “<br>”
Next

The above code will display our session elements. Now let us move to another page and check our session array. You can write the same ( above ) code and display the elements. Now let us learn how to transfer the session array to a local array.

Dim i,my_languages2

my_languages2=session(“my_languages”)

Now we have our my_languages2 as local array storing the value from session array. Now we will loop through and display all the elements of this local array. Before that we will use one if condition checking to know our variable is an array or not .

If IsArray(my_languages2) then

for i=LBound(my_languages2) to UBound(my_languages2)
Response.Write my_languages2(i) & “<br>”
Next

Else
Response.Write ” not an array”
End If

Session Time Out or duration of active session in ASP

As the session variables are stored at server side we can’t keep them for ever. Then how long we can keep the session variables at our server end ? It depends on how frequently or how long the user is interacting with the server. If the interacting period is going on then server has to keep the session variables active but if the user is not active then it will remove the session variables.

The duration within which the visitor must interact with server to keep the session live is 20 minutes by default. But this duration can be changed at script end by this command.

Session.Timeout = 10

The above line will fix the interval for 10 minute and within this time the visitor has to interact with the server to keep the session live. So inside our script we can manage the session time as per our requirement. We can display the session timeout value like this.

Response.Write “Your session will timeout after ” & Session.Timeout & ” Minutes”

File and Directory handling

May29th
2010 Leave a Comment Written by admin

File and Directory handling

Reading data of a file by ASP File system object

Using file System object we can read the content of a file. As we have already discussed FileSystemObject is used to check the presence of the file before we want to read.

While reading the content of the file we can use three different ways to collect the data. One is by specifying number of chars we are interested in collecting or reading.

Response.Write OpenFileobj.Read(3)

The above line will collect 3 characters from the file to read the next 3 again we have to use the same command. As we are not aware of how many characters are present inside the file so we will use a loop to collect all the data in a set of 3 chars. Here we have to check that we have not reached the end of the file. We will get this error message

Error Type:
Microsoft VBScript runtime (0x800A003E)
Input past end of file

If there are two chars left then our last command should collect the two chars and should not try again. To do this we will use command OpenFileobj.AtEndOfStream . This will became true once the file end is reached.

Do While Not OpenFileobj.AtEndOfStream

We can also read line by line by changing the read command to ReadLine. Here is the code to read one line each time.

Response.Write OpenFileobj.ReadLine

Same way we can read all the content of the file by using a single command ReadAll like this

Response.Write OpenFileobj.ReadAll

This is to be used when the file we are reading is not big as this command uses lot of memory to store all the data.

Here is the code used to read the data from a text file. You can see we have used Server.MapPath to map the path of the file we are going to read.

<%
Dim OpenFileobj, FSOobj,FilePath
FilePath=Server.MapPath(“text.txt”) ‘ located in the same director
Set FSOobj = Server.CreateObject(“Scripting.FileSystemObject”)
if FSOobj.fileExists(FilePath) Then
Set OpenFileobj = FSOobj.OpenTextFile(FilePath, 1)

Do While Not OpenFileobj.AtEndOfStream
Response.Write OpenFileobj.ReadLine & “<br>”
Loop

OpenFileobj.Close
Set OpenFileobj = Nothing
Else
Response.Write “File does not exist”
End if
Set FSOobj = Nothing
%>

Determining the existence of file or directory by using FileSystemObject in ASP

We can check whether file of folder exists at a location by using file system object ( FileSystemObject). This is often required to check the existence of a file or directory before using, otherwise system will generate an error message which is not good to display to the visitors. So before using any file or folder we can check the status of them.

FileSystemObject or fso uses physical path of the file or folder to check the existence so before using this we have to convert the virtual path to physical path for our folders or files by using server.mappath object.

We will use one variable to hold the instance of the FileSystemObject and using this we will check the existence of the file or folder.

Dim objFSO
Set objFSO = Server.CreateObject(“Scripting.FileSystemObject”)

Next we will use the If Then Else statement to check the condition of the file or folder.

If objFSO.FolderExists(Server.MapPath(“db”)) Then
Response.Write “Folder Exists”
else
Response.Write “Folder does not exit”
End if

Here “db” is the name of the folder we are checking the existence. We have used the command Server.MapPath to change the virtual path to physical path of the folder db.

We can print the command based the response of the object ( True or False ) and display the message accordingly.

How to get current ASP script running file name without using FileSystem object

We can get the current file name of the asp script without using the FileSystem object. The reason for this is we want to develop a common script which can be used ( or included ) in any file to display various file system properties. The FileSystem object needs the file name as input so we will try to develop this script which can be used as a input to the FileSystem object for further development.

The best example is to develop a script which will display the last modified date of the file. Let us start with how to read the script name in ASP. The code used below will give the file name along with the directory or the path name.

Dim my_array, fname
fname = Request.ServerVariables(“SCRIPT_NAME”)

The above code will display the file name with full path. For example if the present file is in my_file directory and file name is test.asp then the output will be

/my_file/test.asp

To get the file name out of the above full path string we have to break the string and create an array by using split function with “/” as delimiter. Once the array is created we can get the last element of the array to get the file name. Here we will be using Ubound function to get the size of the array and we will use that to get the last element of the array.

Here is the full code to display the current file name

Dim my_array, fullname, fname
Response.Write Request.ServerVariables(“SCRIPT_NAME”) & “<br>”
fullname = Request.ServerVariables(“SCRIPT_NAME”)
my_array=split(fullname,”/”)
fname=my_array(ubound(my_array))
Response.Write fname

How to get last updated & created date and time of an ASP file

We will try to develop a code for showing the last modified date and the created date of the file and display to visitors. This code has to work on it own without any input or changed settings.

We will use the FileSystemObject for getting the last changed or updated along with created date of the file. To make this code universal we will not use name of the file as input to this FileSystemObject , it its place we will use code to get the current file name and then use that as input to FileSystemObject. This way we can make it independent of file name setting and the same code can be used inside any asp file without any changes.

Before reading this it is advisable to read the FileSystemObject and how to get the file name of the current script running page. With this knowledge we can add more code to get the last updated time of the file.

Here is the code to get the current file name and FileSystemObject created.

Dim objFSO, objFile, fname, fullname, my_array
fullname = Request.ServerVariables(“SCRIPT_NAME”)
my_array=split(fullname,”/”)
fname=my_array(ubound(my_array))

Set objFSO = Server.CreateObject(“Scripting.FileSystemObject”)
Set objFile = objFSO.GetFile(Server.MapPath(fname))

To these lines we will add the file name and DateCreated and DateLastModified to get the full code to display the modified time.

Response.Write “Created date of file “& objFile.Name & ” = ” & objFile.DateCreated Response.Write ”
Last Modified date of file “& objFile.Name & ” = ” & objFile.DateLastModified

Getting the list of files inside a directory by using FileSystemObject in ASP

By using FileSystemObject (FSO)we can list out all the files of a directory. Here we will be using server MapPath to map the virtual path to real path as used by file system object. After initiating the object we can instantiate the folder object. We will be using this folder object Files property to get all the files present within the folder.

Before this it is advisable to learn the FileSystemObject, Server MapPath to convert virtual path to real path before reading this.

In our example we have used the folder name my_folder which is inside the directory name t so the path of the folder is

http://mysite.com/t/my_folder/

Here is the code.

Dim objFSO, objFile, objFolder

Set objFSO = Server.CreateObject(“Scripting.FileSystemObject”)
Set objFolder = objFSO.GetFolder(Server.MapPath(“/t/my_folder”))

For Each objFile in objFolder.Files
Response.Write objFile.Name & “<br>”
Next
Set objFolder = Nothing
Set objFSO = Nothing

Displaying last updated date along with the file name
We can add the last modified date of the file by adding the DateLastModified property of the File object. This one line we will add inside the For Each Loop.

For Each objFile in objFolder.Files
Response.Write objFile.Name & ” : ”
Response.Write objFile.DateLastModified & “<br>”
Next

Basic Control Structure

May29th
2010 Leave a Comment Written by admin

Basic Control Structure

Relative and Virtual file Including in ASP

Efficient coding requires reusable common code which gets linked to more than one file. In ASP we will be using file include to add codes inside one external file to our required file. There can be many reasons to use file include inside our ASP scripts, some important requirements we will discuss here.

Menu or links area
Let us say we have a site with more pages ( say one hundred ) and we have added one more page to this site. The link of this section or page has to be connected to all hundred pages so we have to edit all the required pages were the link to this new page is to be added. A better solution is to use one menu.asp file and include the file inside every asp file like this

<!—#include file=”menu.asp” —>


We only have to add our new page link inside the menu.asp file and it will appear all the pages which have included this menu.asp file.

Here the menu.asp file is located in the same directory as the main files calling this include file. If this is inside another directory say my_dir then it has to be included like this.

<!—#include file=”my_dir/menu.asp” —>

Another requirement is to keep the database connecting string. Say your host has given you a set of login id , password and database detail ( known as connecting string ). We will be using database in many files so using the connecting string to connect to database. So rather than keeping this connecting string in each and every file we will keep in one connection.asp file and include this inside all required files. Now this will help us a great when we shift our site to a new host. As the new host give a new connection string we need to change this connection.asp file only. Another way it helps we are maintaining a copy of the site in our local computer with its own connecting string.

Including Virtual
We can include a file located from the root of the virtual directory. Say our connection string is kept at root of our virtual directory. Now from any level the same file can be included like this .

<!– #include virtual = “/connection.asp” –>


Another point we have to keep in mind while keeping sensitive data like connecting string is file extension. If we keep the file name as connection.inc and any one open the file in browser then all the code with database login details will be exposed. So we have to keep these data inside a file with .asp extension.

Include files are always included first before all other codes of main file gets executed. So we can’t keep any condition like if else to dynamically include any file.

If Else and nested If conditional script control

To control the structure and flow of script we use if then else conditional statements of VBScript used in ASP. By using different combinations of if else condition we can control the program execution flow as per requirement. Before going into more details on this let us try the basic syntax of if – condition – Then – Else – Endif syntax.

If condition Then
Script block 1 here if condition is true
Else
Script block 2 here if condition is false
EndIf

In the above script block we have first tested the condition and if it is TRUE then Script block 1 gets executed and if the condition is FALSE then script block 2 is executed.

Here is a simple sample code for printing greatest of two numbers.

Dim n1,n2
n1=25
n2=45
If n1 > n2 Then
Response.Write ” Greatest number is ” & n1
Else
Response.Write ” Greatest number is ” & n2
End If

By changing the assigned values to n1 and n2 we can check how the if else control structure works.

We can keep If conditions inside another If conditions but each If condition has to have matching End If condition. We call it nested If conditions. The above code is changed to add one more If condition inside main If condition.

Dim n1,n2
n1=-25
n2=-45
If n1 > n2 Then
Response.Write ” Greatest number is ” & n1
If n1 < 0 Then
Response.Write ” First number is a negetive number ”
End IF

Else
Response.Write ” Greatest number is ” & n2
End If

Some places we can use ElseIF condition than using more nested If Else condition. Here is an example of uses of ElseIf Condition

Dim my_num
my_num=40
If my_num < 100 Then
Response.Write ” It is less than 100″ & “<br>”
If my_num < 50 Then
Response.Write ” It is less than 50 also” & “<br>”
End If

ElseIf my_num > 200 Then
Response.Write ” It is greater than 200 ” & “<br>”
Else
Response.Write ” This is greater than 100 but less than 200″ & “<br>”
End if

Note that ElseIf doest not require an End If to close but the original If condition should have its own.

ElseIf condition can’t be used just after one Else condition. Where as Else condition can be used before ElseIF condition.

Matching options by using Select Case statement in ASP

In VBScript used in ASP, when we have to match a given variable with more number of possible values, it is better to use Select Case statement. Here the first possible matching value is checked and then the code gets executed.

This Select Case type statement is very common in other scripting languages and they are known differently in different scripts. In php the equivalent statement is SWITCH.

Let us start with the syntax of Select Case statement in ASP

Select Case expression
Case value1
Script part if value1 matches
Case value2
Script part if value2 matches
End Select

Here is the code part in a simple example where a number is stored in a variable and then it is matched with different Cases inside a Select Case statement.

Dim my_num
my_num=150

Select Case my_num
Case 100
Response.Write “It is less than 100″ & “<br>”
Case 150 Response.Write “It is equal to 150 ” & “<br>”
Case 200 Response.Write “It is equal to 200 ” & “<br>”
End Select

The output of the above line is “It is equal to 150”

In the same line while checking for one value we can check for another value by separating it with a coma, like this .

Case 150,160
Response.Write ” It is equal to 150 or 160 ” & “<br>”

If none of the value matches with the variable we have set then we can keep one default value for this by using Case Else. So in the code below the Case Else statement will be executed.

Dim my_num
my_num=160
Select Case my_num

Case 100
Response.Write ” It is greater than 150 equal to 200 ” & “<br>”
Case 150
Response.Write ” It is equal to 150 ” & “<br>”
Case Else
Response.Write ” It is Not equal to any set values ” & “<br>”

End Select

Here the Case Else part will be executed as all other cases will fail to match.

ASP Do While Wend commands syntax

Looping is a common requirement in any scripting language, we will learn here how to use Do While, Until, Loops to manage execution of the code blocks more than once.

Let us start with do While Loop, here the condition is checked for the starting of the loop and the code is executed only if the condition is TRUE. Here is the syntax

Do While Condition
Script block here
Loop

As long as the condition is satisfied ( or True ) the script block will be executed. Always at the starting the Condition is checked. Here is a simple script using Do While loop.

Dim my_num
my_num=1
Do While my_num <=10
Response.Write my_num & “<br>”
my_num = my_num +1
Loop

The above code will print 1 to 10 and it will fail to print 11 as the condition checking will return False. We can modify the Do While loop and keep the condition checking at the end of the Loop.

Do
Script block here
Loop While Condition

Now let us change our old example and try this way.

Dim my_num
my_num=11

Do
Response.Write my_num & “<br>”
my_num = my_num +1
Loop While my_num <=10


Here we can see there is a output of 11 as the inside the loop code is executed once even before the condition is checked and found False. So this way at least once the code inside the Loop will be executed. Test the above code by adding the While condition at the starting of the loop.

Sometime we may try to execute the loop till the condition becomes True. For this we can use Do Until Loop statement. Here is the code.

Dim my_num
my_num=1
Do Until my_num > 10
Response.Write my_num & “<br>”
my_num = my_num +1
Loop

There While … Wend statement for looping also. This is same as Do While Loop.

ASP for Next Commands syntax

We can fix the number of looping across a code block to be done by using for next looping. This is one of the common scripting commands used in different languages. PHP for loop is here. Let us start with the basic syntax of for next loop.

For count_start to count_end step 1
Script block
Next

count_start is the variable stores the initial value of the count, count_end is the final value of the loop and the value of count_start increases by the value of step. Default value of Step is 1. Here is a simple code to display number 1 to 10 by For Next loop.

Dim i
For i=1 to 10
Response.Write i & “<br>”
Next

The code above will print number 1 to 10. We can modify the code by adding a step value of 3 like this.

Dim i
For i=1 to 10 step 2
Response.Write i & “<br>”
Next

The output of the above code is 1 3 5 7 9 with line breaks after end of every number.

Form and request object in ASP

May29th
2010 Leave a Comment Written by admin

Form handling in Asp

Form and request object in ASP

Forms in web pages are very common. We can have signup forms to login forms and many other types of forms in our web pages. Through forms users submit data to the server or interact with the site. This is the way server gets user entered information for further processing. Through a login form when we submit our user id and password, the data reaches the server and is checked against stored user id and password for validation.

Form design is a front end job so html is used to generate different form components to get formatted data from the user. Different form components are used based on the type of data to be entered by the user. For example if the user has to enter the state name of USA then it is better to ask the user to select the state name from a drop down list box (showing the list of states) than asking the user to enter the state name in a input text box.

Once the user submits the form, data processing is done at server side and here we will be using validation at server side scripting language to handle the data. We will learn how to process the form data using ASP ( VBScript ). Such jobs can be handled by other scripting languages like PHP, Perl, JSP etc.

In the form html code we will specify to which page the data is to be send by using action attribute and we will also specify method to tell the form the way data is to be posted. There are two methods to post the data, one is GET and the other one is POST method. Here is the code for basic html form.

<form name=f1 method=post action=file_name.asp>
… form components
</form>

From the above code we can see the method is specified as post and the action is pointing to file_name.asp. So here we will receive the data of the form in file_name.asp page for processing. To handle the form data in receiving page ASP request object is used. Next we will learn how to use

Get method and request object to collect data in ASP

As we have seen in ASP form basics, there is an Request object to handle or receive data of a form in the action page ( page specified in form action attribute ). We will learn how to get data using request object and how the data is posted through query string in GET method.

In GET method data of the form is passed through query string in name and value pairs. The data is separated from the file name by question mark( ? ) and between each pare of name and value ampersand ( & ) symbol is used to separate. Here is the example how in the GET method data is transferred.

You can see in the above query string the form data is kept after the file name and the question mark ( ? ) . Then name and value pairs are used and they are separated by ampersand ( & ). This is the way data is posted using URL or the address bar of the browser window.

Collecting data using Request object in ASP
Once the form is submitted data is available to the page indicated at the action attribute of the form. Here we have to use Request.QueryString to get the value of the data field. To get the name entered by the user in name field here is the code

Dim name
Name=Request.QueryString(name)

Here we declared name as a variable for in the present script and then used Request object to collect the data of the name field. Now name field data is available to the variable name. Same way other data can be collected by using query string.

Here is the code of a form

<form method=get action=my_file.asp>
Your Name<input type=text name=name><br>
Age (years)<input type=text name=age size=3>
<input type=submit value=’Submit Data’>
</form>

Here is the asp code inside my_file.asp file to collect the query string data

Dim name,age
name=Request.QueryString(“name”)
age=Request.QueryString(“age”)
Response.Write (“Welcome ” & name & ” You are ” & age & ” Years Old”)

We can get all the query string data displayed by using for each loop as they are stored as name value pairs. Here is the code. Note that we are not using any individual form component name to collect the data.

Dim var_get
For Each var_get in Request.Querystring
Response.Write var_get & ” = ” & Request.Querystring(var_get) & “<br>”
Next

Post method of form data handling by request object

In POST method of sending form data to processing page is more used than GET method. In POST method data entered inside the form is passed to action page by using HTTP header. The main difference visible here is that data is not passed through URL as a query string in user address bar (like GET method). Here is the form code for method object.

<form name=f1 method=post action=file_name.asp>
… form components
</form>

In POST method data can be collected by using request object of ASP. Here is the code

Dim my_var
my_var=Request(“city”)

Here my_var is a declared variable and city is the form component name where city name is entered by the user. Now the value entered by the user is available at variable my_var

Like in the Get method we can also loop through and display all the name value pairs associated in POST method of form submission. Here is the code

For Each var_get in Request.Form
Response.Write var_get & ” = ” & Request.Form(var_get) & “<br>”
Next


But this is not a good practice of allowing all variables to initialize as this can be exploited to pass unwanted variables into the script.

Collecting checked radio button value of a HTML form in ASP

Radio buttons in a form in ASP is used to collect user’s choice. Here radio button is used when user has to select one of the many options presented. For example we want the visitor should say the mode of transport he select while traveling. Here one of the four options is to be decided by the visitor so we can use radio button here. As a part of the form component radio buttons can be used along with other components of a form. We will discuss here only the handling of radio button in a form and collecting the radio button value through ASP.

A group of radio buttons will have same name but different values. In a form there can be any number of groups of radio buttons but each group of buttons will have same name.

We will try here with one group of radio button giving the visitor to select one choice but same can be extended to more than one group of radio buttons. Here is the code to display a group of radio buttons inside an html form.

<form method=post action=form-radiock.asp>
<input type=radio name=t1 value=’road’>Road
<input type=radio name=t1 value=’rail’>Rail
<input type=radio name=t1 value=’air’>Air
<input type=radio name=t1 value=’ship’>Ship
<input type=submit value=’Submit’>
</form>

As we submit the form the value of the selected radio button will be available at the action page and we can collect the value of this radio button like this.

Dim mode
mode=Request(“t1″)
Response.Write ” Mode of Transport is ” & mode

This way the selected mode of transport will be available for further processing.

Getting the checked values of checkbox Array of a form in ASP

Checkbox are shown to visitors to get the opinion on a fixed value. Sometime the visitors may have to submit more than one choice out of a group of options so here checkbox can be shown to the visitors. For example we can ask the visitor to submit what are the games they play and we can show a list of games. Visitor may select one or more ( or may select all ) games by clicking the checkboxes. Here choice can be more than one ( In case any one to be selected out of the list then radio button is to be used ) so checkbox is the best option. We will learn how to collect the checked values of the form checkbox inside ASP for further processing. Here is the html form with checkboxes.

<form method=post action=form-checkboxck.asp>
<input type=checkbox name=t1 value=’cricket’>Cricket
<input type=checkbox name=t1 value=’football’>Football
<input type=checkbox name=t1 value=’tennis’>Tennis
<input type=checkbox name=t1 value=’hockey’>Hockey
<input type=submit value=’Submit’>
</form>

Here we have used t1 as common name for all the checkbox with different values so they will be treated as a group of checkbox. Once the form is submitted then the values of the checked checkboxes will be available to the action page and can be collected like this.

Dim mode,mode_a,i
mode=Request(“t1″)

We have used t1 as the common name so all the values of the checkbox for which the visitor has checked will be available as Request(“t1″) as comma separated values. So in the above code the variable mode value will be consisting of all checked values separated by comma.

So now let us split the string to get the array of checked values.

mode_a=split(mode,”,”)

Now we will loop through the array by using for for loop and UBound function to print out the checked values of the checkboxes.

For i=LBound(mode_a) to UBound(mode_a)
Response.Write mode_a(i) + “<br>”
Next

Declaring array in ASP

May29th
2010 Leave a Comment Written by admin

Declaring array in ASP

We have seen how to declare variables in VBScript used in ASP. Now we will try to learn how we can declare and use arrays inside ASP code. Let us try using declare one array with fixed number of elements.

Dim myArray(1)

The above line declared a fixed width array. Now we will try to add element to this array.

myArray(0) = “UK”
myArray(1)=”USA”

You can see we have added two elements to this array. As the array starts with 0 element so we can add 2 elements if it is declared like this. Same way myArray(5) can store 6 elements , starting from 0 element.

What happens if we try to add one more element to the above array? We will get error message as we declared the myArray element as fixed number array. To change the number of elements to be stored , we have to declare the array as dynamic size array. But before adding the element we must re-declare the size of the array. Here is the code to declare a dynamic size array.

Dim myArray() ‘Declaring a dynamic array
ReDim myArray(1) ‘Re Declaring a dynamic array
myArray(0) = “UK”
myArray(1)=”USA”

You can see we have re-declared the array with size and then stored elements inside it. Now as we declared this element at the starting as a dynamic array we can re-declare this array with any size. If we are not declaring as dynamic array then we can’t change the size by re-declaring the array. The code below will generate error.

Dim myArray(1) ‘Declaring a fixed array
ReDim myArray(2) ‘Re Declaring the fixed array

Now let us work with adding more elements to an dynamic array. Here we will first declare a dynamic array and then add two elements to it by re-declaring the size of the array. Then we will try to add two more elements to the same array by preserving the old elements. To add more elements we have to use preserve while re-declaring the array like below.

Dim myArray() ‘Declaring a dynamic array
ReDim myArray(1) ‘Re-Declaring a dynamic array

myArray(0) = “UK”
myArray(1)=”USA”
‘Added two elements now let us redeclar and add to more elements
ReDim Preserve myArray(3)
myArray(2)=”Canada”
myArray(3)=”UAE”

For Each item In myArray
Response.Write(item & “<br>”)
Next

We have included the for each loop to display all the element of the array. The output will display all four elements we added now.

Length of an array in ASP by using UBound function

We can get the length or total number of element in the array by using UBound() function. Note that the index of the first element of the array is 0. So if there are five elements inside an array then the function UBound() will return 4. Here is the code to get the highest index of the array. Note that total element is 1 plus the highest index.

Dim myArray(3) ‘Re-Declaring a dynamic array

myArray(0) = “UK”
myArray(1)=”USA”
myArray(2)=”Canada”
myArray(3)=”UAE”
Response.Write (“Total element of the array = ” & UBound(myArray) )

for i=0 to uBound(myArray)
Response.Write “<br>” & myArray(i)
Next

Here UBound is used to set the maximum looping length to display each element of the array.

Creating arrays by breaking strings using split function

We can break a string and create an array by using split() function in ASP ( VBScript). We can decide what way the array to be created by breaking the string. If we break the string by using one space as a delimiter then the array will contain all words of the string. Same way we can take any other delimiter like coma ( , ) or any other character and generate an array by breaking the string. Here is the syntax of split function.

My_Array=split(My_String,” “)


Here My_String is the string variable and we are using one space length as delimiter and breaking the string. We will get our array in the variable My_Array.

We can restrict the total elements of the array by specifying another options parameter to split function. This way the last element will contain rest of the string. This example will make it simple.

My_String=”Welcome to plus2net, learn web programming and design”
My_Array=split(My_String,” “,3)

Here is the value of each item of the array we get after the split function

My_Array[0] = Welcome
My_Array[1] = to
My_Array[2] = plus2net, learn web programming and design

You can see the last element contains all the words of the string.

Here is the full code

Dim My_String
Dim My_Array
My_String=”Welcome to plus2net, learn web programming and design”

My_Array=split(My_String,” “)
For Each item In My_Array
Response.Write(“<br>” & item)
Next

Same way we can create one string by joining all elements of an array by using Join() function.

Join function to add all elements of an array to create string variable in ASP

We can create a string by joining all the elements of an array by using join() function. The out put of this function is a string variable. Here is the syntax of using join() function.

My_String = join(My_Array)

Here My_Array is the array and the My_String is the string variable which gets the string which is returned by join function after adding all the elements of the My_Array array.

While joining by default one blank space is used as delimiter, we can specify any delimiter while joining the elements by using join function. Here is the syntax of this.

my_String=join(myArray,”,”)

This way we can have any delimiter added between the elements while generating the string variable. In the above example comma ( , ) is used.

Here is the complete code for joining elements and creating a string variable.

Dim myArray(3) ‘Declaring a dynamic array

myArray(0) = “UK”
myArray(1)=”USA”
myArray(2)=”Canada”
myArray(3)=”UAE”

For Each item In myArray
Response.Write(item & “<br>”)
Next

my_String=join(myArray,”,”)
Response.Write(my_String & “<br>”)

Searching inside an array for matching elements using Filter function.

We can search inside an array for a string using Filter() built in function of VB used in ASP. The search or find operation will return another array with the result. We can use different arguments to match our requirement while using Filter function. This function works like different types of string functions like InStr, Replace etc. Here is the syntax of Filter() function.

Filter(my_array, search_string, include, comparetype)


Here my_array is our main array inside which we will be searching, search_string is the string variable or the string itself to be searched inside my_array. The other two arguments include and comparetype are optional arguments. include is a Boolean value, it can be True or False. If it is True then all matching elements of the my_array is returned and if it is set to False then all not matching elements are returned. The argument comparetype can take value of 0 or 1, if it is set to 0 then it is a binary comparison so it is case sensitive as a result lower and upper case letters are treated as different. If the value of comparetype is set to 1 then it will be a text comparison so it is case insensitive, as a result lower case and upper case text are treated as same.

Let us try with this simple code on how to use Filter function

Dim myArray(3) ‘Declaring a dynamic array
myArray(0) = “UK”
myArray(1)=”USA”
myArray(2)=”Canada”
myArray(3)=”UAE”

For Each item In myArray
Response.Write(item & “<br>”)
Next
search_string=”UA”
my_filter=Filter(myArray,search_string)

Response.Write “<br>—–After Filter——<br>”
For Each item In my_filter
Response.Write(item & “<br>”)
Next

The output of the above code is here

UK
USA
Canada
UAE
—–After Filter——
UAE

By default the argument include is set to True and comparetype is set to 0. So if we search for lower case word ua ( in place of UA ), we will get empty result. We can add the value of these two optional arguments and see the result. The Filter function can be modified like this

my_filter=Filter(myArray,search_string,True,1)

You will get different results by making include = False and changing comparetype to 0.

MATH FUNCTIONS ASP

May29th
2010 Leave a Comment Written by admin

MATH FUNCTIONS

ASP round function to format decimal place in ASP

Round function is used to round of a number and format the number as per requirment.

Round(5.768) will return 6
Round(5.368) will return 5
Round(0.768) will return 1
Round(-3.368) will return -3

We can format a number as per requirement of decimal place. For example we want the number should display two decimal places only.

Round(5.768,2) will return 5.77

ASP Math Function

Math functions are part of our ASP scripts. Mostly they are used within the applications and support the script with various features. We will discuss some common functions used frequently inside our code.

Int function to get Integer part
From any number we can get the integer part only by using int function . Here are some values returned by int function

Int ( 4.0 ) will return 4
Int ( 4.1 ) will return 4
Int ( 4.9 ) will return 4
Int ( 4.5 ) will return 4
Int ( 1.1 ) will return 1
Int ( 0 ) will return 0
Int ( -0.1 ) will return -1
Int ( -2.1 ) will return -3
Int ( -2.9 ) will return -3

Mod function to get the reminder of division
We can get the reminder after a division is by using mod function. Here is the codeDim

my_num1,my_num2
my_num1=50
my_num2=10

Response.Write my_num1 mod my_num2

The output of above line is 0. If we change the value of my_num1 to 55 then the output will change to 5.

ASP Random number generator

We can generate random number for our applications using ASP. The random number can be used for displaying random images, or random banners or random colors for a page or random numbers for any type of application. To generate random number we have to initiate random number generator first by using randomize function. Here is the code to generate random number between 1 and 10

Dim my_num
Randomize
my_num = Int((rnd*10))+1
Response.Write my_num

The function rnd returns random number between 0 and .9 so we have multiplied it by 10 to move the decimal place one step right. Then took the integer part by using Int function, then we have added 1 to it.

We can also give a range of number and generate random number between the given maximum and minimum numbers. Here is the code.

Dim my_num,max,min

max=5
min=2

Randomize
my_num=int((max-min+1)*rnd+min)
Response.Write my_num

Finding Today date and time and changing the format on location

May29th
2010 Leave a Comment Written by admin

Finding Today date and time and changing the format on location

In ASP using VBScript let us learn how to get present date, time in different formats. As we run ASP as a server side scripting process using VBScript as language, the time or date we will get is the time or date of the server. NOT THE LOCAL TIME OF THE CUMPUTER we are using to access the page. Local time can be found out by using client side JavaScript function for date and time. In ASP we will start with printing present ( today ) date. Here is the format.

d_today=Date

Here d_today is the variable and it will store the value of Date. Here is the code to display the present date.

Dim d_today
d_today=Date
Response.Write d_today

To display the time along with the date we have to use Now.

Dim d_today
d_today=Now
Response.Write d_today

The code above will print todays date along with time Hour: Minute : Second.
To display only time we can use Time function.

D_today=Time

We can change the date format displayed based on our requirement by using SetLocal function. Let us try to display date in UK English format. Here is the code.

Dim d_today,var_Locale
var_Locale = SetLocale(2057) ‘ UK
d_today=Now ‘ Along with time
Response.Write d_today

Display of date and time in local format in ASP using FormatDateTime

We can display Formatted date and time by using FormatDateTime function of VBScript within ASP. This function can take only date , only time or both date and time and display in specified format. Here is the format the function FormatDateTime uses.

FormatDateTime(my_date,Format)

Here my_date is the date variable and Format takes the value of 0 to 4 and format the display based on this. The table at the end of this page displays all possible formats with different value of Format.

Here is the code to use FromatDateTime function.

Dim my_date,var_Locale
var_Locale = SetLocale(1033)
my_date=Now
Response.Write FormatDateTime(my_date,0)

Here the Format value is specified as 0 so the output of this is here .

7/19/2006 8:38:39 PM

For different values of Format ( 0 to 4 ) Here is a table of displays. Note that SetLocale is set to USA format. For other list of LCID value of local formats please see the article on today date and time.

Format Display Type Details
0 vbGeneralDate 7/19/2006 8:38:39 PM Date and Time
1 vbLongDate Wednesday, July 19, 2006 Date in Long format
2 vbShortDate 7/19/2006 Date in m/d/yyyy
3 vbLongTime 9:53:22 PM Long Time
4 vbShortTime 15:53 Short Date

DateAdd function to add date and time

We can add date by using DateAdd function of VBScript using in ASP. We can add any type of value like day, month , year etc using DateAdd function. Here is the syntax for the DateAdd function.

DateAdd ( date_type, increment_by, date)

Here date_type is the type of date to be added. It can be month, year, Day, Hour, minute etc. Different values are available in a table at the end of this tutorial. The argument increment_by is the interval we want to add to the third argument date.

Here is the code explaining the use of DateAdd function.

Dim d_today,d_added
d_today=Date
Response.Write “Today date is ” & d_today & “<br>”
d_added=DateAdd(“yyyy”,5,d_today)
Response.Write “Add 5 Years ” & d_added & “<br>”

In the above code we have added five years to the current date. By changing the value of date_type we can add month, days etc to the present date. Here is the code to add 6 months to today.

d_added=DateAdd(“m”,6,d_today)

DateAdd function will not return any invalid date. Let us try with this example.

d_added=DateAdd(“d”,32,#1/28/04#)

This line will return 2/29/2004,

Now let us change the year to 2003 and see the result

d_added=DateAdd(“d”,32,#1/28/03#)

The output of above line is 3/1/2003
This way we can add different types of dates to an existing date & time.
Table for different date_type values

Value Meaning
“yyyy” Year
“m” Month
“d” Day
“h” Hour
“n” Minute
“s” Second
“w” Weekday
“ww” Week of the year
“q” Quarter

Finding out difference in two dates by using DateDiff function

We can find out the difference between two dates by using DateDiff function of VBScript used in ASP. DateDiff() finds out the difference of the dates based on the required date part like month, year, days etc. Here is the basic syntax of DateDiff function.

DateDiff(date_type, date1, date2, first_dow, first_woy)


Here date_type is the date part to be considered while returning the output. This can be month, day, year etc. The table with different values of date_type is listed at the end. Next two arguments date1 and date2 are two date values for which difference is to be calculated. The other two arguments first_dow and first_woy are optional arguments. First_dow takes the value to specify what is to be taken as first day of the week and the other value first_woy takes the value of first week of the year.

Let us see this example code on uses of DateDiff to find out difference in months between two dates.

Dim d_diff
Response.Write “Today date is ” & d_today & “<br>”
d_diff=DateDiff(“m”,#2/28/03#,#2/28/06#)
Response.Write “Difference ” & d_diff & “<br>”

The output of the above by changing the value of date_type we can find out the difference in days, years, weeks etc. Table for different date_type values

Value Meaning
“yyyy” Year
“m” Month
“d” Day
“h” Hour
“n” Minute
“s” Second
“w” Weekday
“ww” Week of the year
“q” Quarter

Collecting parts of Date by using DatePart function

We can collect part of the date like year, month, day, date, Weekday etc from date by using DatePart function in VBScript used in ASP. We can extract the required date portion from the full date or date variable. Here is the syntax of the DatePart function.

DatePart(date_type, date)

Here date_type is the type of date part we want to get like Day, month, year, week etc. date is the date variable or a fixed date figure. Here is the code to display month part from today’s date.

Dim d_today
d_today=Now
Response.Write DatePart(“m”,d_today)

Above code will return month in number for today’s date. By changing date_type argument to different values we can get year, day , day of the year etc by using this function.

Let us try to collect year from a fixed date . Here is the example

Response.Write DatePart(“yyyy”,#09/10/2003#)

We will get an out put of 2003

We can also get the Date, Month or year by using Day(date), Month(date) and Year(date) function respectively. For example

year(#10/15/2003#)

This will give 2003 as output.

Month(#10/15/2003#)

This will give 10 as output.

Day(#10/15/2003#)

This will give 15 as output.

Getting Name of the Month by entering month number

We can get the months name by using the month number by using MonthName() function.
Here is the syntax for MonthName function.

MonthName(10)

Output of the above code is October.

It can take one more optional argument to return month name in long or short format. By default it is set to False

MonthName(10,False)

This will return October

MonthName(10, True )

This will return Oct

Getting Weekday names by using WeekDay and WeekDayName functions in ASP

From a date variable or from a date we can get the weekday number staring from Sunday as 1 and Saturday as 7 ( see the table at the end ) by using weekday() function. Here is the syntax of weekday function.

WeekDay(#7/25/2006#)

Here we have taken one date but we can also use any date variable as input to the WeekDay function. Like this …

WeekDay(d_mydate)

Here d_mydate is a date variable and we can assign any date value to it.

The output of this function will be between 1 and 7 depending on the weekday of the input value. The example

WeekDay(#7/25/2006#)

The output of above line is 3. It represents Tuesday of the week. To get directly the name of the weekday we can use WeekDayName() function. This function takes the number of weekday and returns the name of the weekday. Here is the syntax of WeekDayName() function

WeekDayName(weekday_number, type)

Here weekday_number is the variable holding the weekday number, type is an optional Boolean argument to specify long or short name of the weekday to be returned. False value of type returns Long name and True value returns short name. By default it is set to False. Here are some examples of WeekDayName function.

Response.Write WeekDayName(4)

Response.Write WeekDayName(4,True)

This will give output Wed

Response.Write WeekDayName(5,False)

Table for WeekDays function values

Value Meaning
1 Sunday
2 Monday
3 Tuesday
4 Wednesday
5 Thursday
6 Friday
7 Saturday

Generating Date variables by using DateSerial function in ASP

By dateserial function in VBScript used in ASP we can generate date variable by using different variables for day, month and year. This is a quite useful as we can take different user input and create a date variable out of it. We can’t create a date variable by placing the variables within two # marks. Like this

My_date=#my_month, my_day,1985#

The above code will give error message. Let us start with the syntax of dateserial function.

DateSerial(yyyy, dd, mm)

The above function takes three inputs month, date and year and generates a date variable. The date variable then can be used for normal operations. Here is an example of generating date variable.

Dim d1, d2, d3
d1=”2007″
d2=”2″
d3=”28″
Response.Write DateSerial(d1,d2,d3)

The above code will return 2/28/2007.

DateSerial can be used to generate different dates before or after the day entered. Here is an example to get next day of the given date.

Response.Write DateSerial(d1,d2,d3+1)

Same way we can get the date variable for one month before the dates like this

Response.Write DateSerial(d1,d2-1,d3)

For five years advance date, here it is

Response.Write DateSerial(d1+5,d2,d3)

DateSerial function takes care of leap years also. Check this code again

Dim d1, d2, d3
d1=”2007″
d2=”2″
d3=”28″
Response.Write DateSerial(d1,d2,d3+1)

We will get 3/1/2007 as output but if we change the value of year to 2008 ( d1=”2008″) then the out put will change to 2/29/2008

DateSerial function is mostly used to collect user enter data and generating a date variable out of it.

Function IsDate to check valid date or date variable

We can check (or validate) the date variable or a date by using IsDate() function. User entered date values in a form are to be checked for correct date or not before further processing. This function takes one input and gives output as TRUE or FALSE based on the input. A valid date or date variable will return TRUE or it will return FALSE. Here is the syntax of IsDate() function.

IsDate(my_date)

Here my_date is a date variable or a date itself. Out put of IsDate function is either True or False. Here is the complete code of IsDate() function.

my_date=”02/28/2007″
Response.Write my_date & ” = ” & IsDate(my_date)

Here IsDate function will return True. If we change the variable my_date like this.

My_date=”02/29/2007″

Then the output of IsDate() function will be false.

IsDate function is useful where user entered date value is to be checked for a valid date for further processing. Whatever date entered by the user through a form can also be checked by using this function.

User entered date value validation in ASP

We can collect date values from user and check the inputs for a valid date or not by using IsDate () function. Here we will give the options to the user to select month, date and year from list boxes and text box and then create a date variable using it. Then we will check the date variable and find out it is a valid date or not.

We will display a message accordingly saying correct date or not.

Here is the code below to check the user entered date value

<%@ Language=VBScript %>
<% Option Explicit %>

<html><head>
<title>(Type a title for your page here)</title>
</head>
<body bgcolor=”#ffffff” text=”#000000″ link=”#0000ff” vlink=”#800080″ alink=”#ff0000″>

<%

Dim todo
todo=Request(“todo”)
if todo=”submit” then
Dim month, dt, year, my_date
month=Request(“month”)
dt=Request(“dt”)
year=Request(“year”)
my_date=year + “/” + month + “/” + dt
if(IsDate(my_date)) then
Response.Write month + “/” + dt + “/” + year & ” is a valid date ”
Else
Response.Write month + “/” + dt + “/” + year & ” is a Not a valid date ”

End If
End If
%>
<form method=post name=f1 action=”><input type=hidden name=todo value=submit>
<table border=”0″ cellspacing=”0″ >
<tr><td align=left >

<select name=month value=”>Select Month</option>
<option value=’01′>January</option>
<option value=’02′>February</option>
<option value=’03′>March</option>
<option value=’04′>April</option>
<option value=’05′>May</option>
<option value=’06′>June</option>
<option value=’07′>July</option>
<option value=’08′>August</option>
<option value=’09′>September</option>
<option value=’10′>October</option>
<option value=’11′>November</option>
<option value=’12′>December</option>
</select>

</td><td align=left >
Date<select name=dt >
<option value=’01′>01</option>
<option value=’02′>02</option>
<option value=’03′>03</option>
<option value=’04′>04</option>
<option value=’05′>05</option>
<option value=’06′>06</option>
<option value=’07′>07</option>
<option value=’08′>08</option>
<option value=’09′>09</option>
<option value=’10′>10</option>
<option value=’11′>11</option>
<option value=’12′>12</option>
<option value=’13′>13</option>
<option value=’14′>14</option>
<option value=’15′>15</option>
<option value=’16′>16</option>
<option value=’17′>17</option>
<option value=’18′>18</option>
<option value=’19′>19</option>
<option value=’20′>20</option>
<option value=’21′>21</option>
<option value=’22′>22</option>
<option value=’23′>23</option>
<option value=’24′>24</option>
<option value=’25′>25</option>
<option value=’26′>26</option>
<option value=’27′>27</option>
<option value=’28′>28</option>
<option value=’29′>29</option>
<option value=’30′>30</option>
<option value=’31′>31</option>
</select>

</td><td align=left >
Year(yyyy)<input type=text name=year size=4 value=2006>
<input type=submit value=Submit>
</table>
</form>

</body>
</html>

Checking for patterns and validating the user inputs using Regular Expression

May29th
2010 Leave a Comment Written by admin



Checking for patterns and validating the user inputs using Regular Expression

Regular expressions is a powerful object of VBScript to use in any string matching and particularly in pattern matching. This is highly important to maintain data uniformity and prevents any malicious code or characters to enter to the system other than the required patterns.

If user inputs are not validated the attackers can use this to get entry inside the protected area and this is known as injection attack.
For example we don’t want any one to use any character inside the field specified for entering zip or pin code inside a form. Same way for a phone number we may allow hyphens (- ) and numbers but not characters. User id should contain only number and characters and it should be minimum 3 and maximum 8 char length. We can check one valid email address by checking the pattern used.

Regular Expression is a big subject and there are different ways to match patterns here. More details can be found at Microsoft MSDN home page and at regular expression tutorial

We need to first initiate the VBScript regular expression object and here is the code for that.

dim RExp : set RExp = new RegExp

We will see the use of this object in our examples for validating different inputs.
Let us start with some simple validations using regular expression.

Validating for user id & password: Here we will allow only characters and numbers within a minimum and maximum length

Validating Email address

Validating date entered by users

Validating zip code

Validating telephone number

Checking user id and password for only character and numbers using Regular Expression

We can check the entered user id of any user within a web form by using Regular Expression. This is to prevent user or attacker to use other characters and codes in the input field. Here we will check for special characters but checking for special characters and then for length is a bit lengthy process so we will check for existence of characters, numbers and number of characters used.

We can imitate the regular expression object of VBScript like this.

dim RExp : set RExp = new RegExp

By using this object we can check any string.

Here is the complete code. The output of this is true or false based on the result of validation.

Dim userid
dim RExp : set RExp = new RegExp
with RExp
.Pattern = “^[a-zA-Z0-9]{3,8}$”
.IgnoreCase = True
.Global = True
end with
userid= “a234f678″
Response.Write RExp.test(userid)

Here only characters lower or upper case along with numbers is allowed. The length of the string has to be minimum 3 and maximum 8 char length. Here is some different values of the string ( userid ) for which the validation will pass and output will be True.

A234f678, a23, a2345f, a2345f6

It will fail or return False for these values

A2, a2345f6789, a23*5,a234f5/6


Checking email address for pattern using Regular Expression

Here we can check the email address for valid or not by using Regular Expression. Note that we are not checking the existence of email address or the domain name associated with it, we are only checking the pattern of the email and it is in acceptable pattern or not.

Every email address will have one name part and another domain part which includes the domain extension. The name part and the domain part is separated by a @ character. In the name part we can’t allow special characters other than underscore ( _ ) , Hyphen ( -) and dot ( . ) . So our validation has to take care of this. In the domain name part underscore ( _ ) not allowed and Hyphens ( – ) allowed but they can’t be at the starting or ending of the domain name.

We can imitate the regular expression object of VBScript like this.

dim RExp : set RExp = new RegExp

By using this object we can check any string.

Here is the complete code. The output of this is true or false based on the result of validation.

Dim email
dim RExp : set RExp = new RegExp
with RExp
.Pattern = “^([0-9a-zA-Z]([-.\w]*[0-9a-zA-Z])*@([0-9a-zA-Z][-\w][^_]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,9})$”
.IgnoreCase = True
.Global = True
end with
email= “a2.3_ra-bi@domain_name.com”
Response.Write RExp.test(email)

Here only characters lower or upper case along with numbers is allowed. The length of the string has to be minimum 3 and maximum 8 char length. Here is some different values of the string ( userid ) for which the validation will pass and output will be True.

a2.3_ra-bi@domain-name.mobiccccc, a2.3_ra-bi@domain-name.co.in, a2.3_ra-bi@domain-name.co.in

It will fail or return False for these values

a2.3_ra-bi@domain-name.com2c, a2-bidomain-name.com, a2rabi@domain_name.com

Connecting to Access database using ADO

May29th
2010 Leave a Comment Written by admin

Connecting to Access database using ADO

We will be using ActiveX Data Objects (ADO) to create a connection to Access database. ADO model contains six objects and we will be using Connection String to connect to database.

Connecting String
Creating a Connection String using ADO and opening the connection To connect to Access database we can create a connection object by using ADO. Here is an example of connection object creation and opening the connection object.

Set objconn = Server.CreateObject(“ADODB.Connection”)
objconn.ConnectionString = “DRIVER=Microsoft Access Driver (*.mdb);DBQ=” & Server.MapPath(“db/months.mdb”)
objconn.Open


Note that here we have using server MapPath to locate the access database. Here database is stored inside db directory relative to the script running this code. Now we have opened the connection to the access database next is we need one object to handle records.

Recordset Object
To handle records of a MS access table we need recordset object provided by ADO. Using this object we can get a subset of records of our table. We can declare Record set object like this.

Set objRs = Server.CreateObject(“ADODB.Recordset”)

By just declaring the recordset object we can’t handle data, we need to open it and during the opening process we can give different arguments to handle the recordset object. Here is the syntax of opening a Recordset object.

Recordset.Open Source, Connection, cursortype, locktype, commandtype


As you can see above we have used different arguments and let us try to understand each one with some examples.

Source
This can be the table name or sql query or some other types.

Connection
Connection which we have established before

Cursourtype
This tells how the recodset will move. By default it is forward only.

Locktype
This tell how we handle the record. As there will be more than one client trying to access / update the data. By default it is read only.

Commandtype
Tells how the source parameter to be evaluated. adCmdTable Tells that the source is a table. Let us try to display all month names stored in an access table.

Recordset object property in ASP to browse through the records

We will learn how to collect data from an Access table and display them. We have seen before how to connect to Access table and how to open a recordset object. We will discuss here some methods and properties of recordset object to handle data.

While opening the recordset object we define different parameters and based on that we can handle the data collected by recordset object. Based on the query we apply our recordset object will fetch data for us. Recodset object maintain a pointer to this set of records and this pointer always points to one row or one record at a time. We can move to different locations in different directions by using methods associated with recordset object. We will try to understand some of the methods here.

EOF This is a Boolean value that gets the value True if the record pointer is at the end of a set of records. This property is often used while displaying all records of the recordset object by looping through. Each time at the beginning of the loop EOF property is checked and record is displayed ( inside the loop ) if EOF is not true.

BOF Like EOF (explained above )BOF gets TRUE value if recordset is pointing to the first record of the set of records the recordset object is having.

MoveNext: This moves the pointer by one step in forward direction. It will generate an error if record pointer is at the last record or the EOF property is true.

MovePrevious: This moves the recordset pointer by one step backward. This depends on the Cursourtype we declare at the time of opening the recodset object. We can’t use MovePrevious for a forward-only cursor. MovePrevious will return error if BOF property is TRUE.

MoveFirst: With this we can move the pointer to beginning of the set of records.

MoveLast: Goes to the last record

Move number: Goes (or jumps) to the number of record from the current pointer position.

We will use all the above discussed properties to collect records and display them row wise in our next tutorial.

Displaying records of an Access table

We can display records of a table by looping through all the records of a recordset object. Recordset object properties are discussed before. We have to connect to our Access table using connecting string before collecting our records.

Now let us use our emp table where we have stored our employee details. This table has four fields. Filed name emp_no stores the unique employee number of the employee. Then Name field stores the name of the employee, desg field stores the designation of the employee then the last one dept field stores the department name of the employee.

Using connecting string we can connect and then we will use one sql command to select records from the table.

Set objconn = Server.CreateObject(“ADODB.Connection”)
objconn.ConnectionString = “DRIVER=Microsoft Access Driver (*.mdb);DBQ=” & Server.MapPath(“db/emp.mdb”)
objconn.Open
strSQL = “SELECT * FROM emp_m ”

After opening the recordset object we will use recordset properties and then we will use Do Wile loop to loop through the records of the recordset. Here at the beginning of the each loop the condition of EOF is checked and if NOT TRUE then the loop is executed. Inside the loop we display two fields of each record by using their filed names like this.

Response.Write objRs(“emp_no”) & ” ” & objRs(“name”) & “<br>”

This way all the records are displayed and the loop ends if the last record is shown. This is the simplest way to display records of a access table. Here is the output of the script.

145 John Reid
245 Peter Horn
175 Rabin Pack
187 Ran Keth

Here is the complete code

Dim objconn,objRS,strSQL
Set objconn = Server.CreateObject(“ADODB.Connection”)
objconn.ConnectionString = “DRIVER=Microsoft Access Driver (*.mdb);DBQ=” & Server.MapPath(“db/emp.mdb”)
objconn.Open

Set objRs = Server.CreateObject(“ADODB.Recordset”)
strSQL = “SELECT * FROM emp_m ”
objRS.Open strSQL, objconn

Do While Not objRS.EOF
Response.Write objRs(“emp_no”) & ” ” & objRs(“name”) & “<br>”
objRS.MoveNext
Loop
objRs.Close
objconn.Close

Dynamically listing drop down list options with table data

We can populate a drop down list box by taking data from an access database. This way we get the advantage of handling the data in database itself and managing the data through query. From this we will understand how data is collected from a database and added as elements of a drop down list box. For example we have used our employee table. We have tried here to collect the department’s names from the table and created the list box.

Note that in our employee table there are many employees in any one department so same department name appears many time inside the table. To display the department name only once we have to use distinct query command in our select query .
Try to understand how html drop down list box works in our html section. Now we will try to format our drop down list box with the returned data from the table. There is a tutorial on how to get data from database and display them in browser. We will combine this and develop our list box. We are not discussing the connecting string, and data objects and on how to fetch data here.

Data is collected by record set object and looped to display all records. Within this loop we will try to format the list box. Out side the loop we will declare the list box and then within the loop we will add the formatted list box options.

Response.Write “<select name=dept><option value=”” selected>Departments</option>”
Do While Not objRS.EOF
Response.Write “<option value=”” & objrs(“dept”) &””>”& objRs(“dept”) &”</option>”
objRS.MoveNext
Loop
Response.Write “</select>” The above code will format the data returned from the table for the drop down list box. This is how we can create a list box with the value form a table. Now let us see the full code of the file.

<%@ Language = VBscript %>
<% Option Explicit %>
<!– #include virtual = “/adovbs.inc” –>
<% Response.Buffer = True %>
<html>
<head>
<title>Database Search</title>
</head><body>

<%
Dim objconn,objRS,strSQL

Set objconn = Server.CreateObject(“ADODB.Connection”)
objconn.ConnectionString = “DRIVER=Microsoft Access Driver (*.mdb);DBQ=” & Server.MapPath(“db/emp.mdb”)
objconn.Open

Set objRs = Server.CreateObject(“ADODB.Recordset”)
strSQL = “SELECT distinct(dept) FROM emp_m ”
objRS.Open strSQL, objconn
Response.Write “<select name=dept><option value=”” selected>Departments</option>”
Do While Not objRS.EOF
Response.Write “<option value=”” & objrs(“dept”) &””>”& objRs(“dept”) &”</option>”
objRS.MoveNext
Loop
Response.Write “</select>”
objRs.Close
objconn.Close

%>
</body>
</html>


Changing second list components based on first list value

We have seen how to populate a drop down list box by taking data from a table. Now we will design two drop down list boxes and try to learn how to manage options of the second drop down list box based on the selection of the first drop down list box. There are many such requirements where user select the value in first list and then second list changes to show available options under the selected data of first list. For example if we have a list of states of USA in the first list and the cities list in the second list, then on selection of a state from first list the second list should change to show only the cities of selected state in USA.

Another example is our employee table. In first drop down list box the name of the departments will appear. As we select a department from the first list the second list should show the employees of the selected department only. You can see how the first department list is populated by taking data from the Access table in our dynamic population of list box tutorial . Such requirements are very common and often used in different web sites.

This particular script reloads the browser on selection of the first drop down list box and sends the data back to server. From server the options of the second list box are managed. So we will be using server side scripting languages to manage the operation.

Here we will be using VBScript under ASP environment to develop this script. The same functionality of managing two dropdowns is also developed by using PHP and is available with demo in our PHP section. This can be managed by using client side JavaScript also. The tutorial on managing list boxes at client side using JavaScript is available at JavaScript section. Here the list boxes are managed without sending back the data to server or reloading the page.

Read how Ajax is used to manage two drop down lists in PHP section.

We will not discuss on how to connect to db, how to display data or how to populate list box with table data here. ( It is advisable to learn all these before reading this tutorial ).

We will keep one JavaScript function within the head tag of our page. The main job of this javascript function is to reload the page with the selected data of the first drop down box. Note that as we are using JavaScript to reload the page so we can add a section to check the status of JavaScript ( enabled or disabled ) of the client browser.

Here is the JavaScript function within our head tag.

<SCRIPT language=JavaScript>
function reload(form){
var val=form.dept.options[form.dept.options.selectedIndex].value;
self.location=’emp.asp?dept=’ + val ;
}
</script>

The above code gets executed once the first drop down list box is selected, it collects the selected value of the first drop down list box ( here it is dept ) and then redirects the page with the value of department in the query string. Note that our file name is emp.asp, so once the department name is selected, then the url at the address bar should look like this.

Now the selected value of the dept is to be collected from the query string by using Request object.
dept=Request.QueryString(“dept”)

So this way we can get the value of the department and store it in the variable dept.

Now let us create object connection and record set. We will not discuss much on this as the tutorials are available here.

Set objconn = Server.CreateObject(“ADODB.Connection”)
objconn.ConnectionString = “DRIVER=Microsoft Access Driver (*.mdb);DBQ=” & Server.MapPath(“db/emp.mdb”)
objconn.Open

Set objRs = Server.CreateObject(“ADODB.Recordset”)


strSQL = “SELECT distinct dept from emp_m”

Now let us populate the drop down list box by taking data from the table.

objRS.Open strSQL, objconn
Response.Write “<form method=post name=f1 action=”><select name=dept onchange=’reload(this.form)’><option value=”>Select dept</option>”
Do While Not objRS.EOF
Response.Write “<option value=” & objRs(“dept”) & “>” & objRs(“dept”) & “</option>”
objRS.MoveNext
Loop
objRs.Close
Response.Write “</select>”

Note that we have used onchange event handler for the first drop down list box to execute the JavaScript function reload() once an option is selected. This drop down list ( first list ) always shows same elements. Now let us move to second drop down list, where the elements changes based on the value of first list. We will do a check for the variable dept before adding it to the query for second list. We will check the length of the dept variable by using len function of ASP. If the length of the variable is more than 0 that mean there is a department name stored inside. Here is the code for the second drop down list.

If len(dept) > 1 Then

strSQL = “SELECT * FROM emp_m where dept=’” & dept &”‘”
objRS.Open strSQL, objconn

Do While Not objRS.EOF
Response.Write objRs(“emp_no”) & ” ” & objRs(“name”) & ” ” & objRs(“dept”) & “<br>”
objRS.MoveNext
Loop
Response.Write “</form>”
objRs.Close

objconn.Close
end if

Note that The second list is populated once the value for dept is stored by selection of the first list.

What Is ASP?

May29th
2010 Leave a Comment Written by admin

What Is ASP?

“Active Server Pages” abbreviated as ASP, is a server-side scripting environment developed by Microsoft. Using ASP, we can create and run dynamic and interactive web server applications. With ASP, we can combine HTML pages, script commands, and COM components to create interactive Web pages or powerful Web-based applications, which are easy to develop and modify.
The default scripting language used for writing ASP is VBScript although we can use JavaScript. All ASP pages will be executed at the server and the page will have the extension “.asp”.
An ASP page cannot run by simply opening it in a web browser. The page must be requested through a web server that supports ASP, this is why ASP stands for Active Server Pages, no server, no active pages.
When a browser requests an ASP page, the web server interprets any ASP contained within the web page before sending the HTML produced to the browser. In this way, the entire ASP is run on the web server and no ASP will ever be passed back to the web browser.

Installing ASP

Just as we have seen before, for running ASP we need a web server, which need not be an external. We can install web server in our PC. Microsoft provides web servers such as Personal Web Server (PWS) which can be run on any Windows95/98, NT or 2000 workstation and Internet Information Server (IIS) for Windows NT or Windows 2000 based web servers.
Installing Personal Web Server (PWS)
Personal Web Server ships with Windows 98 CD, you can find it in add-ons folder present in the Windows 98 CD. If you are using Windows 95, you have to download “Windows NT 4.0 Option Pack” from Microsoft.

  1. Insert your Windows 98 CD into your CD-ROM Drive.
  2. Explore your CD-ROM Drive.
  3. Open “add-ons” folder, there you will find “pws” folder, run “setup.exe” from this folder.
  4. Follow the instructions on the screen to install “Personal Web Server”

After installation of PWS, you will find a PWS icon on your desktop and most probably a small icon of PWS in the right corner of the taskbar. Open any one of them. If the PWS is running then you will see an option “Stop PWS” or else you will see “Start PWS”.
To check if PWS is running, open your Internet Explorer. In the URL box enter http://127.0.0.1 or http://localhost and press Enter. If everything is working fine, you will see a default page generated by PWS. If you can see any page then PWS is running correctly or else you have to restart your computer and start PWS again and continue the same process. Hopefully everything will be alright now.
Installing IIS on Windows 2000:
Microsoft Internet Information Server (IIS) is a web server that integrates into the Windows NT Server so no need to download from any where. If you haven’t install IIS during installation of Windows 2000, then follow the below steps to install IIS.

  1. From Start Button, go to Settings and Control Panel.
  2. In the Control Panel, select Add/Remove Programs, in that Select Add/Remove Windows Components.
  3. In the wizard, check Internet Information Services, click Ok. After this, an Inetpub folder will be created where you can find a folder named wwwroot.

Now your installation process is over. If you want to check whether IIS is running or not, Open Internet Explorer and type http://localhost in the address bar. If everything is working fine, it will display the default page generated by IIS. If not,

  1. Go to Control panel. Open Administrative Tools and double click “Internet Information Server”.
  2. Select “Default Web Site” and Click on the Start button present in the toolbar.

Basic file structure of ASP

After installing IIS the web server let us start our first ASP page. Here we assume that ASP engine is working perfectly and server root is set to proper directory were we will keep our fist asp page. Here if the directory path is E:\myfiles\ and our first ASP file name is test.asp then the path becomes E:\myfiles\test.asp. To open this file in web browser mode we have to open this as

http://localhost/test.asp
or
http://127.0.0.1/test.asp

Note that in IIS we have set the default directory to E:\myfiles\

Now with this settings let us go for our fist file test.asp

We will start with our ASP code beginning mark <% and end the code with %> . This way we will tell our ASP engine to execute the ASP part of the code within the <% and %> symbol and send the other codes as it is to the browser. So we will start with telling the server that the code we are going to use is VB Script. ASP is not a script or language , it is a technology server uses. So we have to tell the server which language we are using. We can also use JavaScript as server side script. But mostly VBScript is used for server side scripting requirements and we will also use this. Here is the way we will tell to use VBScript language for processing.

<%@ Language=VBScript %>

In the next line we will tell that all the variables used here are to be declared before using. This has some advantage as we move to words developing complex applications using ASP. This is a good practice to follow. So here is our next line

<% Option Explicit %>

After this we will keep our html meta tags and then we will go to the body section of the ASP page. We will try to print the message “Hello World” to the screen. Here we will store this message string in a variable and let us name the variable as msg. Please note that we have told ASP engine that all the variables we use are to be declared before, this we have told in the second line of our code by saying <% Option Explicit %> . So we will declare the variable by using the command Dim. Here is the example

Dim msg
msg=”Hello World”

Now let us print the message or the variable to the screen by using Response.Write object.

Response.Write msg

That’s our entire first ASP example. Here is the complete code.

<%@ Language=VBScript %>
<% Option Explicit %>

<html>
<head>
<title>(Type a title for your page here)</title>
</head>

<body >

<%
Dim msg
msg=”Hello World”
Response.Write msg
%>

</body>
</html>

Syntax for declaring variables in ASP

ASP ( VB Script ) provides also easy use of variables but some of the basic syntax is to be followed. One of the biggest advantage of ASP variables is it is not case sensitive. If I declare a variable as my_var then I can still access the same variable by calling it as My_var.

We also have to follow some syntax for declaring variables.

All variables declared must start with a letter. Number or any other key are not accepted as variable. So variable name like 1my_var is not accepted but my1_var is accepted.

Length of the variable name should not exceed 255 characters.

Space period and dashes are not allowed within the variable name.

Reserve words are not allowed. Example we can’t declare response as a variable

The best way is to be use descriptive variable names for easy understand of the purpose and identification. Birth date variable should be declared as variable like birth_date

We will use more ASP code and see the use of variables in other tutorials.

Getting the variable type and checking in ASP

In ASP we can check what type of ( data ) variable it is before using. We can use the function VarType to display a value for associated with each type of variable. This value is a number so linking this number to type of data is to be done. There is another function TypeName which displays the Data type directly without any associated value.

We can check for a specific type by using the function isArray, isDate etc functions. These are useful while developing code for further processing while working with variables.
Let us start with some syntax of TypeName function.

Dim v1 ‘Declaring variable v1
v1=”Welcome” ‘assigning value
Response.Write “Value of v1=” & v1
Response.Write “<br> v1 is a <i>” & TypeName(v1) & “</i> variable ”

In the above code we have declared v1 as a variable and assigned a string data to it. So now the variable v1 became string variable. So we will get an output like this by using the above code.

Value of v1=Welcome
v1 is a String variable

We can change the value of v1 to different values and see the type of variable TypeName function returns.

We can create a double variable and check with isArray function to get true or false. Here is the code for this.

Dim v1 ‘Declaring variable v1
v1=”Welcome” ‘assigning value
Response.Write “Value of v1=” & v1
Response.Write “<br>is v1 an array? <i>” & isArray(v1) & “</i> ”

The output of the above code is shown here.

Value of v1=Welcome
is v1 an array? False

Advantage of using ASP and where to use

ASP is a server side script and it can perform many backend processing jobs for a web site, same way it can’t do many things particularly the client end operations as it has no control over the client end events or user controls. So there are many advantages and disadvantages of using ASP to manage web pages. We may not like to say disadvantages of ASP and it is better to say the limitation of any server side scripting language, as these limitations are faced by other scripting languages like PHP, JSP, Perl etc. We will try to understand where ASP can be used and where it should not be used.

Using server side scripting language like ASP we can manage the content of any page and such dynamic code ( or content ) for the web browsers can be generated based on various conditions we set in our ASP program. To a visitor the back end script or processing is of no use. They are more interested in design, content, speed etc. So there is no point in asking ASP engine to work when there is simple html content to be displayed at browser end. This will also improve the loading speed of the page. The user browser does not understand scripts we run at server. Brower understands JavaScript (if enabled), html, CSS etc. So what ever output we want to be send to the browser has to be written using these languages. So the task we want to be performed at client end can’t be written at server end using ASP.

ASP engine finishes its job of processing the code and then send the codes to users browser. From this point on words till again the page request comes back to server, there is no control of ASP on the page. So we should not expect ASP to perform some tasks which are likely to happen at the client browser end. This will be clear when we discuss some of the task and where ( client or server side ) the task is to be completed and which script will take care of it. There are some tasks we can do at both the ends and the situation on which they are to be used we will try to discuss in next page.

Where to use ASP and where not to use ASP

There are many jobs to be performed and we will try to understand what type of job we should do at server end and what we will delegate to client end JavaScript or HTML. Let us start with some tasks we want our web page to do. Here are some of the common jobs we will discuss to get an idea on what to use for different tasks a web page perform.

Displaying Alert message in a small window
Small windows are client side property. So we need Client Side JavaScript to display the alert message. But the content of the alert message we can manage by using ASP. We can conditionally ( display or not ) show the alert box and manage the content ( text part ) based on ASP code we write. So let us conclude that showing an alert message is client side task and we have to use JavaScript for this.

Authenticating user before entering to members only area
This task we can’t handle at client end. Once the user enters userid and password, we will verify that using a membership table and then we can say the user is allowed or not. This job is to be handled by ASP script running at server end. Now displaying the welcome message or asking the member to try again is decided by ASP script and the display is shown at browser by using html tags.

Validating data entered by user in a text box ( or form )
This we have seen at many web sites. If we are suppose to enter price in figure and if we enter any character in the text box then we get an error message. Here validation of the data entered by the user is done and accordingly error message is displayed. This task can be done at server side and client side also. Depending on the requirements we can develop the code. There is a risk if we do it at client end only. If script execution is off at client end then the validation code written using client side JavaScript is not going to check and display any error message. This will allow un-validated data to enter into system. However we can check the browser setting of the client computer and display a message or redirect to a page asking them to enable the script execution first before using the form. Depending on server side validation is full proof but for bigger forms large amount of data has to return again from server if data validation fails. This is going to take more time particularly for the visitors with slow connection. So validation is used based on requirements of the page.

We have discussed three common applications here and we will able to understand more on this as we develop scripts for different applications.

Different requirement for redirecting users

We redirect the user to different pages or different site based on the condition or based on user selection. We may need different pages to be executed under different conditions. Some time visitor goes to different pages by clicking different links available on the page. But here we will learn how to redirect the user based on our program or our requirement. There can be many reasons to go for a redirection. Here are some of the common reasons for going for a redirection.

Server side form validation
We submit a form with data and we can design a server side form validation to check the user entered data. If the data entered by the user is not in required format or not as per standards then we may ask the visitor to feed the data again. So here we will send back the visitor to the same form page again showing the error message and asking the visitor to try again.

Sending users to different sections based on the permission level
In a portal we may have different areas marked for different types for users and we want the users to go directly to assigned area after they submit their identity ( may be by login ) . Here without any trigger from user end system will redirect the user to a page for there use.

End of a process.
Some time after submitting a data or after a forum posting you want the visitor to be redirected to display a Thank You message. We can have a common thank you page or an error page where we can redirect the browser.

We will discuss header redirection here. Read more on the same topic in PHP section header redirection.

Header Redirection precaution
One main care we have to take care before giving any header redirection is no data to be posted to the user browser before the header redirection command is applied. We can do our script processing and before sending any output to the browser we will redirect the user. Sometime we may not have any output intentionally posted before the redirection but under various condition some time error message the script will return, resulting in error message saying header already send.

Here is the common error message given by ASP engine if header is already sent and script example of header redirection using Response object.

Redirecting user by using response object in ASP

We can do header redirection in ASP by using Response object. Read the basics of header redirection requirements in different condition. Response object takes the url of the site to which the browser is to be redirected. It can be any full URL like http:www. sitename.com or it can be a relative url if within the site. Here is the basic syntax of the Response.Redirect

Response.Redirect “http://www.itsyllabus.com/“

We can’t apply redirect command if we have already posted any data to the browser. In such a case ASP engine will return error like this .
Response object error ‘ASP 0156 : 80004005′
Header Error
redirect.asp, line 15
The HTTP headers are already written to the client browser. Any HTTP header modifications must be made before writing page content.

So we have to take care that our redirection command should work before any data is posted to browser.

Printing double quotes in ASP

In ASP VBScript we can’t print a double quote inside at output statement. We have to take special care to display a double quote inside or outside a string.

(In PHP we can easily escape the double quote by using escape character ( like \” ) ).

Here are some examples to display double quotes in ASP

We can use chr(34) to print a double quote to the screen

Response.Write chr(34)

( Try different values of chr to display different characters to the screen )

We can use “ to print double quotes to the screen

Response.Write “”"

Some time within a string we will have double quotes to print. Here to print one double quote we will escape it by one more double quote so two double quotes are to be used. Read this line.

Response.Write “Raju told “”ASP is a better scripting language”"”

The above line will print

Raju told “ASP is a better scripting language”

Mark the use of two double quotes within the string to display single double quotes.

Some time we have to display some variable or strings with double quotes within a table cell. Here is a code to display session id inside a table cell.

Response.Write “<tr><td>session(“”userid”")</td><td>”

The output of the above is

session(“userid”)