ASP – Application Object

An application on the Web may be a group of ASP files. The ASP 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 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 changes will automatically be reflected on all pages.

 

Store and Retrieve Application Variables

Application variables can be accessed and changed by any page in the application.

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

<script language=”vbscript” runat=”server”>

 

Sub Application_OnStart

application(“vartime”)=””

application(“users”)=1

End Sub

 

</script>

In the example above we have created two Application variables: “vartime” and “users”.

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

There are

<%

Response.Write(Application(“users”))

%>

active connections.

 

Loop Through the Contents Collection

The Contents collection contains all application variables. You can loop through the Contents collection, to see what’s stored in it:

<%

dim i

For Each i in Application.Contents

Response.Write(i & ”
“)

Next

%>

If you do not know the number of items in the 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) & ”
“)

Next

%>

 

Loop Through the StaticObjects Collection

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

<%

dim i

For Each i in Application.StaticObjects

Response.Write(i & ”
“)

Next

%>

 

Lock and Unlock

You can lock an application with the “Lock” method. When an application is locked, the users cannot 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

%>

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

 

The #include Directive

You can insert the content of one ASP file into another 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 in an ASP page, place the #include directive inside comment tags:

<!–#include virtual=”somefilename”–>

or

<!–#include file ="somefilename“–>

The Virtual Keyword

Use the virtual keyword to indicate a path beginning with a virtual directory.

If a file named “header.inc” resides in a virtual directory named /html, the following line would insert the contents of “header.inc”:

<!– #include virtual =”/html/header.inc” –>

The File Keyword

Use the file keyword to indicate a relative path. A relative path begins with the directory that contains the including file.

If you have a file in the html directory, and the file “header.inc” resides in html\headers, the following line would insert “header.inc” in your file:

<!– #include file =”headers\header.inc” –>

Note that the path to the included file (headers\header.inc) is relative to the including file. If the file containing this #include statement is not in the html directory, the statement will not work.

You can also use the file keyword with the syntax (..\) to include a file from a higher-level directory.

 

Tips and Notes

In the sections above we have used the file extension “.inc” for included files. Notice that if a user tries to browse an INC file directly, its content will be displayed. If your included file contains confidential information or information 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 also 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:

<%

fname=”header.inc”

%>

<!–#include file=”<%=fname%>”–>

You cannot open or close a script delimiter in an INC file. This script will not work:

<%

For i = 1 To n

<!–#include file=”count.inc”–>

Next

%>

But this script will work:

<% For i = 1 to n %>

<!–#include file=”count.inc” –>

<% Next %>

The Global.asa file is an optional file that can contain declarations of objects, variables, and methods that can be accessed by every page in an ASP application.

Reference : Dilip Kumar Jena ( https://mstechexplore.wordpress.com )

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