<asp:Repeater...> <asp:ImageButton ID="image_Edit" runat="server" ImageUrl="~/AP/icon_delete.gif" onclick="button_test_Click"  /> </asp:Repeater>

   protected void button_test_Click(object sender, EventArgs e)
        {
        }

<asp:Button ID="button1" runat="server" CommandArgument="MyVal1"
   CommandName="ThisBtnClick" OnClick="MyBtnHandler" />


protected void MyBtnHandler(Object sender, EventArgs e)
{
     Button btn = (Button)sender;
          switch (btn.CommandName)
          {
                case "ThisBtnClick":
                    DoWhatever(btn.CommandArgument.ToString());
                    break;
                case "ThatBtnClick":
                    DoSomethingElse(btn.CommandArgument.ToString());
                    break;
           }
}