Callback Configuration

This article explains how to configure the RadXmlHttpPanel's callback:

1. Add RadXmlHttpPanel ASP.NET AJAX to the page.

2. Set the EnableClientScriptEvaluation property to true to enable the evaluation of scripts loaded by the controls within the XmlHttpPanel.

3. Place a Label control inside the RadXmlHttpPanel.

4. Handle the ServiceRequest server-side event of RadXmlHttpPanel.

5. In the handler method, add the following code:

   C#

   protected void RadXmlHttpPanel1_ServiceRequest(object sender, Telerik.Web.UI.RadXmlHttpPanelEventArgs e)
   {
       Label1.Text = "Label updated by XmlHttpPanel callback at: " + DateTime.Now.ToString();
   }
   

   VB

   Protected Sub RadXmlHttpPanel1_ServiceRequest(sender As Object, e As Telerik.Web.UI.RadXmlHttpPanelEventArgs)
       Label1.Text = "Label updated by XmlHttpPanel callback at: " + Now.ToString()
   End Sub
   

6. Create an <input/> of type button that will call the set_value client method of the XmlHttpPanel, on a button click. You can also access the callback value from the client on the server using the e.Value property in the ServiceRequest event. Here is how the page and its code-behind should look after completing the steps above:

   ASP.NET

   <telerik:RadScriptManager ID="RadScriptManager1" runat="server">
   </telerik:RadScriptManager>
   <telerik:RadXmlHttpPanel runat="server" ID="RadXmlHttpPanel1" EnableClientScriptEvaluation="true"
       OnServiceRequest="RadXmlHttpPanel1_ServiceRequest">
       <asp:Label ID="Label2" runat="server"></asp:Label>
   </telerik:RadXmlHttpPanel>
   <br />
   <br />
   <br />
   <input type="button" value="Set Value" onclick="SetValue();return false;" />
   <script type="text/javascript">
       function SetValue()
       {
           var panel = $find("<%=RadXmlHttpPanel1.ClientID %>");
           panel.set_value("string_value");
       }
   </script>
   

   C#

   protected void RadXmlHttpPanel1_ServiceRequest(object sender, Telerik.Web.UI.RadXmlHttpPanelEventArgs e)
   {
       Label1.Text = "Label updated by XmlHttpPanel callback at: " + DateTime.Now.ToString();
       //access the callback value from the client on the server using the e.Value property
       Label1.Text += "<br/> The returned value fron the client's set_value() function is: <strong>" + e.Value + "</strong>";
   }
   

   VB

   Protected Sub RadXmlHttpPanel1_ServiceRequest(ByVal sender As Object, ByVal e As Telerik.Web.UI.RadXmlHttpPanelEventArgs)
       Label1.Text = "Label updated by XmlHttpPanel callback at: " + DateTime.Now.ToString()
       'access the callback value from the client on the server using the e.Value property
       Label1.Text += "<br/> The returned value fron the client's set_value() function is: <strong>" + e.Value + "</strong>"
   End Sub