I had not found a alternative for asp:updatepanel.update() in RadAjaxPanel
How the senario is possible with RadAjaxpanel
Bellow is a code sample
<asp:UpdatePanel ID="updatePanelSearch" runat="server" UpdateMode="Conditional"> <ContentTemplate> <asp:Label ID="Label1" runat="server" Text="Search"></asp:Label> <telerik:RadTextBox ID="radtxtSearch" runat="server"> </telerik:RadTextBox> <asp:ImageButton ID="imgbtnSearch" runat="server" ImageUrl="~/Images/Search.png" OnClick="imgbtnSearch_Click" /> </ContentTemplate> </asp:UpdatePanel><asp:UpdatePanel ID="updatePanelGrid" runat="server" UpdateMode="Conditional"> <ContentTemplate> <asp:PlaceHolder ID="phGrid" runat="server"></asp:PlaceHolder> </ContentTemplate> </asp:UpdatePanel>protected void imgbtnSearch_Click(object sender, ImageClickEventArgs e) { updatePanelGrid.Update(); /*Update Grid*/ .......... /**/}