control not working after using update panel

Question

I am using update panel for dropdownlist with providing triggering statement and also set autopostback property is "true" but still the DDL control not proper working on selectedindexedchanged.

 

my code is below-->

 

<asp:UpdatePanel runat="server">
<ContentTemplate>
<asp:DropDownList ID="ddlClient" runat="server" Width="99%"
AutoPostBack="True"
onselectedindexchanged="ddlClient_SelectedIndexChanged">
</asp:DropDownList>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="ddlClient"
EventName="SelectedIndexChanged" />
</Triggers>
</asp:UpdatePanel>

 

my .cs file-->

 

 try
{

if (ddlClient.SelectedItem != null)
{

Boolean members = objClsClient.checkmember(ddlClient.SelectedValue);
if (members == true)
{
Image2.ImageUrl = "~/Images/green-flag.jpg";
Image2.ToolTip = "Indimnity Bond Signed";
}
else if (members == false)
{
Image2.ImageUrl = "~/Images/red-flag.jpg";
Image2.ToolTip = "Indimnity Bond Signed";
}

}
else
{

}

 }catch....

 

 

Thanks in advance!!!!!