Introduction
The Global.asax, also known as the ASP.NET application file, is located in the
root directory of an ASP.NET application. This file contains code that is
executed in response to application-level and session-level events raised by
ASP.NET or by HTTP modules. You can also define 'objects' with application-wide
or session-wide scope in the Global.asax file. These events and objects declared
in the Global.asax are applied to all resources in that web application. The
Global.asax is an optional file. If a user requests the Global.asax file, the
request is rejected.
About Global.asax page
Adding a Global.asax to your web project is quiet simple. Open Visual Studio
2005 or 2008 > Create a new website > Go to the Solution Explorer > Add New Item
> Global Application Class > Add.
Now we will have three Application Event Handlers and two Session Event
Handlers.
Here is the list of Application Event Handlers:
Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
' Code that runs on application startup
End Sub
Sub Application_End(ByVal sender As Object, ByVal e As EventArgs)
' Code that runs on application shutdown
End Sub
Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)
' Code that runs when an unhandled error occurs
End Sub
Here is the list of Session Event Handlers:
Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)
' Code that runs when a new session is started
End Sub
Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)
' Code that runs when a session ends.
' Note: The Session_End event is raised only when the sessionstate mode
' is set to InProc in the Web.config file. If session mode is set to StateServer
' or SQLServer, the event is not raised.
End Sub
Note: About Session Event Handlers will learn in next article.
Application Event Handlers
Application_Start():
It gets fired when the first resource is requested from the web server and the
web application starts.
Application_End():
It gets fired when the web application ends.
Application_Error():
It gets fired when an error occurs.
Working with Global.asax file
<%@ Application Language="VB" %>
<script runat="server">
Sub Application_Start(ByVal sender As Object, ByVal e As EventArgs)
Application("HitCount")
= 0
'
Code that runs on application startup
End Sub
Sub Application_End(ByVal sender As Object, ByVal e As EventArgs)
'
Code that runs on application shutdown
End Sub
Sub Application_Error(ByVal sender As Object, ByVal e As EventArgs)
'
Code that runs when an unhandled error occurs
End Sub
Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)
'
Code that runs when a new session is started
End Sub
Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)
'
Code that runs when a session ends.
'
Note: The Session_End event is raised only when the sessionstate mode
'
is set to InProc in the Web.config file. If session mode is set to StateServer
'
or SQLServer, the event is not raised.
End Sub
</script>
Working with Default.aspx file
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="Default.aspx.vb" Inherits="_Default"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD
XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Create
and Use Application Level Events in ASP.Net</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<strong>
Total Hits:
</strong>
<asp:Label ID="Label1" runat="server" Text="Label" Width="247px" Font-Size="Large"ForeColor="Red">
</asp:Label>
</div>
</form>
</body>
</html>
Working with Default.aspx.vb file
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Application("HitCount")
= Application("HitCount")
+ 1
Label1.Text = Application("HitCount")
End Sub
HAVE A HAPPY CODING!