SUMMARY
This article discusses the locations where the
AutoEventWireup attribute can be used, the values that the
AutoEventWireup attribute accepts, and how to use the
AutoEventWireup attribute effectively in Microsoft ASP.NET Web Forms.
AutoEventWireup is an attribute of the
@ Page directive. The
AutoEventWireup attribute may have a value of
true or
false. The value is set to
false when you create a new ASP.NET Web Application. This article
describes how to set and to change the default values of the
AutoEventWireup attribute. This article also describes some of the options of
this attribute by using examples of the ASP.NET Web Forms code that is written
in Microsoft Visual C# .NET.
You may use the
AutoEventWireup attribute to code ASP.NET Web Forms and Web User Controls. When
you set the value of the
AutoEventWireup attribute to
true, the code in ASP.NET Web Forms and in Web User Controls is
simple. However, when you use the
false value in certain circumstances, you may receive better
performance.
You can specify a default value of the
AutoEventWireup attribute in several places:
- The Machine.config file
- The Web.config file
- Individual ASP.NET Web Forms (.aspx files)
- Web User Controls (.ascx files)
When you set the value of the
AutoEventWireup attribute to
true, the ASP.NET runtime does not require events to specify event
handlers like the
Page_Load event or the
Page_Init event. This means that in Visual C# .NET, you do not have to
initialize and to create the delegate structures.
When you use
Microsoft Visual Studio .NET, the value of the
AutoEventWireup attribute is set to
false and the designer automatically generates event handlers.
This article describes the default settings of the
AutoEventWireup attribute and shows you some helpful code.
back to the topRequirements
This
article assumes that you are familiar with the following topics:
- Programming in ASP.NET
- Programming with Microsoft Visual C# .NET
The
following list outlines the recommended hardware, software, network
infrastructure, and service packs that you need:
- Microsoft Visual Studio .NET 2002 or Microsoft Visual
Studio .NET 2003
back to the topConfiguration of
the AutoEventWireup attribute default values
The
AutoEventWireup attribute can be declared in the <pages> section in the
Machine.config file or the Web.config file. In either of these XML-based files,
use the following syntax:
<configuration>
<system.web>
<pages autoEventWireup="true|false" />
</system.web>
</configuration> If you make these changes in the Machine.config file, the changes
affect all ASP.NET Web Forms on the computer. If you make these changes in the
Web.config file, the changes affect only the application that it belongs to.
To change the value of the
AutoEventWireup attribute in the individual ASP.NET Web Form, add the
AutoEventWireup attribute to the
@ Page directive, as follows:
<% @Page AutoEventWireup="true" %>
back to the topWhen the value of the AutoEventWireup attribute is false
If you want to manually hook up events to an event handler, set
the value of the
AutoEventWireup attribute to
false. The following sample shows the code that you can use to handle
the
Load event of the
Page object in an ASP.NET Web Form:
- Start Microsoft Visual Studio .NET.
- On the File menu, point to
New, and then click Project.
- In the New Project dialog box, under
Project Types, click Visual C# Projects.
Under Templates, click ASP.NET Web
Application.
- In the Location box, type the project name
as
http://ServerName/MyWebApp.
Note Replace ServerName with the name of a
server. MyWebApp is the name of a sample ASP.NET Web Application. - In Solution Explorer, right-click the
WebForm1.aspx file, click Rename, and then
type EventWireUpFalse.aspx.
- Replace the existing code in the EventWireUpFalse.aspx file
with the following code:
<%@ Page Language="C#" AutoEventWireup="false" Inherits="MyWebApp.EventWireUpFalse" %>
<HTML>
<HEAD>
<title>Visual C# .NET WIRE-UP FALSE</title>
</HEAD>
<BODY>
<p><% Response.Write(message); %></p>
</BODY>
</HTML> - Replace the existing code in the EventWireUpFalse.aspx.cs
file with the following code:
using System;
namespace MyWebApp
{
public class EventWireUpFalse : System.Web.UI.Page
{ public string message;
private void Page_Load(object sender, System.EventArgs e)
{
message="The Page_Load Event Fired with AutoEventWireup False";
}
// Visual C# .NET requires that you override the OnInit function,
// adding a new delegate for the Page_Load event.
override protected void OnInit(EventArgs e)
{
this.Load += new System.EventHandler(this.Page_Load);
}
}
}
- On the Debug menu, click
Start to build and to run the ASP.NET Web
application.
In this example, you receive a message when the ASP.NET
page framework raises the Page_Load event handler. If the value of the AutoEventWireup attribute is set to false, you must override the OnInit function, and then you must add a new delegate for the Page_Load event handler.
back to the topWhen the value of the AutoEventWireup attribute is true
When you set the value of the
AutoEventWireup attribute to
false, you must manually hook up events to event handlers. When you set
the value of the
AutoEventWireup attribute to
true, the ASP.NET page framework can automatically raise events. The
following sample describes how to code a
Page_Load event handler in an ASP.NET Web Form when the value of the
AutoEventWireup attribute is
true.
- Start Microsoft Visual Studio .NET.
- On the File menu, point to
New, and then click Project.
- In the New Project dialog box, under
Project Types, click Visual C# Projects.
Under Templates, click ASP.NET Web
Application.
- In the Location box, type the project name
as
http://ServerName/MyWebApp.
Note Replace ServerName with the name of a
server. MyWebApp is the name of a sample ASP.NET Web Application. - In Solution Explorer, right-click the
WebForm1.aspx file, click Rename, and then
type EventWireUpTrue.aspx.
- Replace the existing code in the EventWireUpTrue.aspx file
with the following code:
<%@ Page Language="C#" AutoEventWireup="true" Inherits="MyWebApp.EventWireUpTrue" %>
<HTML>
<HEAD>
<title>Visual C# .NET WIRE-UP TRUE</title>
</HEAD>
<BODY>
<p><% Response.Write(message); %></p>
</BODY>
</HTML> - Replace the existing code in the EventWireUpTrue.aspx.cs
file with the following code:
using System;
namespace MyWebApp
{
public class EventWireUpTrue : System.Web.UI.Page
{ public string message;
private void Page_Load(object sender, System.EventArgs e)
{
message="The Page_Load Event fired with AutoEventWireup True";
}
}
} - On the Debug menu, click
Start to build and run the project.
In this example,
you receive a message when the ASP.NET page framework raises the Page_Load event handler. If the value of the AutoEventWireup attribute is true, you do not have to override the OnInit function, and you do not have to add a new delegate for the Page_Load event handler.
back to the topWhen to avoid setting the value of the AutoEventWireup attribute to true
If performance is a key consideration, do not set the value of the
AutoEventWireup attribute to
true. The
AutoEventWireup attribute requires the ASP.NET page framework to make a call to
the
CreateDelegate function for every ASP.NET Web Form page. Instead of using
automatic hookup, you must manually override the events from the page. For more
information, visit the following Microsoft Developer Network (MSDN) Web site:
back to the topOther places where you can use
the AutoEventWireup attribute
The
AutoEventWireup attribute is also an attribute of the
@ Control directive that is used in Web User Controls (.ascx) pages. You
can use the
AutoEventWireup attribute in ways that are similar to those that are described in
this article.
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top