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When we create a new ASP.NET Web Application in Visual Studio .NET, as mentioned earlier, by default, the value of the AutoEventWireup attribute is set to false in the .aspx page and event handlers are automatically created. We can find this in the InitializeComponent method:
this.Load += new System.EventHandler(this.Page_Load);
The best way to see the working of this attribute would be:
Declare a string variable msg as public in WebForm1.aspx.cs.
In the HTML section of WebForm1.aspx, enter the following code in the <Head> section:
<% Response.Write(msg); %>
In the Page_Load, you could enter a value for the variable msg declared.
msg= "We are in Page_Load()";
On running the application, you will get the message We are in Page_Load() [hereafter referred to as message]. Note: this is in the default case where the attribute is set to false.
Now try commenting the event handler code for the Page_Load in the aspx.cs file; and set the AutoEventWireup attribute to false in the .aspx page. On running the application this time, you will not get the message.
Now with the event handler code for the Page_Load in the aspx.cs file still commented; set the AutoEventWireup attribute to true in the .aspx page. On running the application this time, you will get the message.
Reason: In the case where AutoEventWireup attribute is set to false (by default), event handlers are automatically required for Page_Load or Page_Init. However, when we set the value of the AutoEventWireup attribute to true, the ASP.NET runtime does not require events to specify event handlers like Page_Load or Page_Init.
A thing to be kept in mind is that the AutoEventWireup attribute of the Page directive is set to true by default for the machine (check out the value of this attribute in the machine.config) but set to false by default for a .aspx page). So if it is missing, since by default it is true (i.e., at the machine level), the page framework calls page events automatically, specifically the Page_Init and Page_Load methods. In that case, no explicit Handles clause or delegate is needed.
Performance Issues
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