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° ASP (ACTIVE SERVER PAGES)
TUTORIAL-----------------------------------------------------------------------------

ASP Application Object

A group of ASP files that work together to perform some purpose is called an application. The Application object in ASP is used to tie these files together.

Application Object

An application on the Web is a group of asp files. The files work together to perform some purpose. The Application object in ASP is used to tie these files together.

The Application object is used to store variables and access variables from any page, just like the Session object. The difference is that all users share ONE Application object, while with Sessions there is one Session object for each user.

The Application object should hold information that will be used by many pages in the application (like database connection information). This means that you can access the information from any page. It also means that you can change the information in one place and the new information will automatically be reflected on all pages.

Store and Retrieve Variable Values

Application variables must be created in the Global.asa file, but they can be accessed and changed by any page in the application.

You can create Application variables in Global.asa like this:

In the example above we have created two Application variables: The first is named vartime, and the second is named whoon.

You can access the value of an Application variable like this:

There are
<%
Response.Write(Application("whoon"))
%>
active connections.

Looping Through the Contents

You can loop through the "Contents" collection, to see the values of all the Application variables:

<%
dim i
For Each i in Application.Contents
Response.Write(Application.Contents(i) & "<br>")
Next
%>

If you don't know how many items are stored in a "Contents" collection, you can use the "Count" property:

<%
dim i
dim j
j=Application.Contents.Count

For i=1 to j
Response.Write(Application.Contents(i) & "<br>")
Next
%>

Looping Through the Objects

You can loop through the "StaticObjects" collection, to see the values of all the objects stored in the Application Object:

<%
dim i
For Each i in Application.StaticObjects
Response.Write(Application.StaticObjects(i) & "<br>")
Next
%>

Lock and Unlock

You can lock an application with the "Lock" method. When an application is locked, the users can not change the Application variables (other than the one currently accessing it). You can unlock an application with the "Unlock" method. This method removes the lock from the Application variable:

<%
Application.Lock
'do some application object operations
Application.Unlock
%>

ASP Including Files

The #include directive is used to create functions, headers, footers, or elements that will be reused on multiple pages.

The #include Directive

It is possible to insert the content of another file into an ASP file before the server executes it, with the #include directive. The #include directive is used to create functions, headers, footers, or elements that will be reused on multiple pages.

How to Use the #include Directive

Here is a file called "mypage.asp":

<html> 
<body> 
<h3>Words of Wisdom:</h3>
<p><!--#include file="wisdom.inc"--></p> 
<h3>The time is:</h3>
<p><!--#include file="time.inc"--></p>
</body> 
</html>

Here is the "wisdom.inc" file:

"One should never increase, beyond what is necessary,
the number of entities required to explain anything."

Here is the "time.inc" file:

<%
Response.Write(Time)
%>

If you look at the source code in a browser, it will look something like this:

<html>
<body>
<h3>Words of Wisdom:</h3>
<p>"One should never increase, beyond what is necessary,
the number of entities required to explain anything."</p>
<h3>The time is:</h3>
<p>11:33:42 AM</p>
</body>
</html>

Syntax for Including Files

To include a file into an ASP page, place the #include directive and the virtual or file keyword inside comment tags:

"Somefilename" is the name of the file you want to include.

Using the Virtual Keyword

The "virtual" keyword allows you to include files from another virtual directory under the same web server.

As an example: if a file named "header.inc" resides in the root directory, the following line inserts the contents of "header.inc" into an ASP file:

Note: The virtual keyword should be used when you want to use the include files on several pages in different web sites under the same web server.

Using the File Keyword

The "file" keyword allows you to include files from the same directory as the including page or from that directory's subdirectories.

As an example: if an ASP file resides in the same directory as a file named "header.inc," it can insert the contents of "header.inc" like this:

<!--#include file ="header.inc"-->

Note: The file keyword should be used when you want to use the include files on several pages within one web site.

Differences Between the File and Virtual Keyword

<!--#include virtual="/asp/header.inc"-->

The line above includes a file named "header.inc" from asp's directory, even if the file with this statement is in the /ado/text folder.

<!--#include file="/asp/header.inc"-->

The line above will fail from ado's directory.

The line above will succeed from ado's directory.

Tips and Notes

In the sections above we have used the file extension ".inc" for the included files. Notice that if a user tries to browse an ".inc" file directly, its content will be displayed. So if your included file contains source code you do not want any users to see, it is better to use an ".asp" extension. The source code in an ".asp" file will not be visible after the interpretation.

An included file can include other files, and one ASP file can include the same file more than once.

Important: Included files are processed and inserted before the scripts are executed.

The following script will not work because ASP executes the #include directive before it assigns a value to the variable:

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