Update Pannel

 
<asp:ScriptManager EnablePartialRendering="true"
 ID="ScriptManager1" runat="server"></asp:ScriptManager>
 <asp:UpdatePanel ID="UpdatePanel2" runat="server"
 UpdateMode="Conditional">
 <ContentTemplate>
 <asp:Label ID="Label2" runat="server" ForeColor="red" />
 </ContentTemplate>
 <Triggers>
 <asp:AsyncPostBackTrigger ControlID="Button1" EventName="Click" />
 </Triggers>
 </asp:UpdatePanel>

 <asp:UpdatePanel ID="UpdatePanel1" runat="server"
 UpdateMode="Conditional">
 <ContentTemplate>
 <asp:Label ID="Label1" runat="server" /><br />
 <asp:Button ID="Button1" runat="server"
 Text="Update Both Panels" OnClick="Button1_Click" />
 <asp:Button ID="Button2" runat="server"
 Text="Update This Panel" OnClick="Button2_Click" />
 </ContentTemplate>
 </asp:UpdatePanel>