AJAX :: Gridview Control In Side Update Panel

I have gridview with SelectedIndexChanged event.

when I click on a record in gridview it should call the SelectedIndexChanged event and do some operations.

SelectedIndexChanged event is working OK, but when I put the gridview inside ajax updatepanle SelectedIndexChanged event will not response even if I add AsyncPostBackTrigger trigger for SelectedIndexChanged event.

<%@ Page Title="" Language="C#" MasterPageFile="~/Master.Master" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="IMAM_APPLICATION.WebForm1" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">
<div id="mydiv">
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<br /> <br />
<br />
<asp:GridView ID="GridView1" runat="server"
style="position:absolute; top: 280px; left: 30px; height: 240px; width: 915px;"
PageSize="5"
onselectedindexchanged="GridView1_SelectedIndexChanged"
AutoGenerateColumns="False" DataKeyNames="idcontact_info">
<Columns>
<asp:CommandField ShowSelectButton="True" />
<asp:BoundField AccessibleHeaderText="Midle Name" DataField="Midle_Name" />
<asp:BoundField DataField="Last_Name" HeaderText="Last Name" />
<asp:BoundField DataField="Phone_home" HeaderText="Phone Home" />
<asp:BoundField DataField="cell_home" HeaderText="Mobile Home" />
<asp:BoundField DataField="phone_work" HeaderText="Phone Work" />
<asp:BoundField DataField="cell_Work" HeaderText="Mobile Work" />
<asp:BoundField DataField="Email_Home" HeaderText="Personal Home" />
<asp:BoundField DataField="Email_work" HeaderText="Work Email" />
</Columns>
</asp:GridView>
<br />
<br />
<br /></ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="GridView1"
EventName="SelectedIndexChanged" />
</Triggers>
</asp:UpdatePanel>
<asp:RadioButton ID="rdoSearchFlat" runat="server"
style="position:absolute; top: 565px; left: 70px;" Text="Flat Search"
GroupName="Search"/>
<asp:TextBox ID="txtSearch" runat="server"
style="position:absolute; top: 560px; left: 170px;" ></asp:TextBox>
<asp:Button ID="btnSearch" runat="server" Text="Search"
style="position:absolute; top: 555px; left: 375px;"
CausesValidation="False" onclick="btnSearch_Click"/>
<asp:Label ID="Label7" runat="server" Style="position: absolute; top: 630px; left: 85px;"
Text="First Name"></asp:Label>
<asp:TextBox ID="txtFirstName" runat="server" Style="top: 630px; left: 185px; position: absolute;
height: 22px; width: 128px">
</asp:TextBox>
</div>
</asp:Content>