How you can add an event handler?

Using the Attributes property of server side control.

e.g.

btnSubmit.Attributes.Add(“onMouseOver”,”JavascriptCode();”)

In ASP.NET, you can add an event handler in several ways, depending on the context and the control you’re working with. Here are a few common methods:

1. Using the ASP.NET Markup (Web Forms): In ASP.NET Web Forms, you can define event handlers directly in the markup using the OnEvent attribute. For example:
   aspxCopy code

   <asp:Button ID="btnSubmit" runat="server" Text="Submit" OnClick="btnSubmit_Click" />


   In this example, btnSubmit_Click is the name of the event handler method.

2. Using the Handles Keyword (VB.NET): In VB.NET, you can use the Handles keyword to associate event handlers with controls. For example:
   vbCopy code

   Protected Sub btnSubmit_Click(sender As Object, e As EventArgs) Handles btnSubmit.Click
' Event handling code here
End Sub

3. Using the += Operator (C#): In C#, you can use the += operator to subscribe to an event. For example:
   csharpCopy code

   protected void Page_Load(object sender, EventArgs e)
   {
   btnSubmit.Click += btnSubmit_Click;
   }

   protected void btnSubmit_Click(object sender, EventArgs e)
{
// Event handling code here
}


4. Using Code-Behind (Web Forms): You can also define event handlers in the code-behind file (.aspx.cs or .aspx.vb) and wire them up in the code-behind.
   csharpCopy code

   protected void Page_Load(object sender, EventArgs e)
   {
   btnSubmit.Click += btnSubmit_Click;
   }

   protected void btnSubmit_Click(object sender, EventArgs e)
{
// Event handling code here
}


These are some of the common ways to add event handlers in ASP.NET. The choice of method depends on the specific requirements and coding practices of your project.