<telerik:RadAjaxManager ID="RadAjaxManager1" runat="server">
<AjaxSettings>
<telerik:AjaxSetting AjaxControlID="Panel1">
<UpdatedControls>
<telerik:AjaxUpdatedControl ControlID="Panel1" LoadingPanelID="RadAjaxLoadingPanel1"></telerik:AjaxUpdatedControl>
</UpdatedControls>
</telerik:AjaxSetting>
</AjaxSettings>
</telerik:RadAjaxManager>
<asp:Panel ID="Panel1" runat="server" Height="380px" CssClass="background1">
<telerik:RadButton RenderMode="Lightweight" ID="Button2" runat="server" Text="Click to see the loading image" OnClick="Button2_Click"></telerik:RadButton>
</asp:Panel>
<telerik:RadAjaxLoadingPanel ID="RadAjaxLoadingPanel1" runat="server">
Loading panel
</telerik:RadAjaxLoadingPanel>
Imports System
Imports System.Web.UI.WebControls
Imports Telerik.Web.UI
Public Class Test
Inherits InheritedPage
Protected Sub Button2_Click(ByVal sender As Object, ByVal e As EventArgs)
'simulate longer page load
System.Threading.Thread.Sleep(2000)
End Sub
End Class