Hi rajeesh,
You are getting this error because the compiler doesn't find the Button1_Click event.
That means, when you declare your markup like
<asp:Button runat="server" id="Button1" Text="Save" OnClick="Button1_Click" />
The matching event handler in your code would look like
C#
protected void Button1_Click(object sender, EventArgs e)
{
}
VB.Net
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs)
End Sub
Please verify this.