Use Div Click Event As UpdatePanel's Trigger

I'm using a div as an Image button, as the ASP Imagebutton was causing a flash on click, no matter what.

The Div click raises a server side event to bind the grid and it works good. Just that the whole page loads. In order not to, I tried to have it as a trigger.

Now, it gives the error - 'div1 being reistered through RegisterAsyncPostBackControl or RegisterPostBackControl must implement either InamingContainer,IpostBackDataHandler, or IpostbackEventHandler'

ASPX:

<div id="div1" runat="server" class="search"></div>
<asp:UpdatePanel runat="server" updatemode="conditional">
<Triggers>
  <asp:AsyncPostBackTrigger ControlID="divSearch" EventName="Click"/>
</Triggers>
<ContentTemplate>
  <asp:gridview....../>
</ContentTemplate>
</asp:UpdatePanel>

C#:

public partial class Home: System.Web.UI.Page, IPostBackEventHandler
{

    protected void Page_Load(object sender, EventArgs e)
     {
       div1.Attributes["onclick"] = ClientScript.
                                  GetPostBackEventReference(this, "div1_Click");
     }

    protected void div1_Click()
     {
       bindGrid();
     }

    public void RaisePostBackEvent(string eventArgument)
    {
      if (!string.IsNullOrEmpty(eventArgument))
      {
        if (eventArgument == "div1_Click")
          {
            div1_Click();
          }
      }
    }
}

Any way to make this work?