RadAjax for ASP.NET
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MasterPages: initiating requests from one ContentPlaceHolder and loading/updating controls in another Send comments on this topic.
AJAX Manager > How-To > MasterPages: initiating requests from one ContentPlaceHolder and loading/updating controls in another

Glossary Item Box

RadAjaxManager could handle all the MasterPage and WebUserControls scenarios no matter the complexity of the application. To prove this, we show you how it can handle a scenario, where loading of WebUserControls is done in contents of MasterPage by RadAjaxManager.

An important point to notice in the following implementation, is the event bubbling approach. We use it because we load dynamically a user control from an action in another loaded user control. So the button click event is bubbled from the user control to the content page, where the first user control is loaded on each page load. Then we determine whether to perform loading of the second user control depending on the command from the button's bubbled event.

Here is the full working code containing a MasterPage, content page and two simple WebUserControls:

 

MasterPage ASPX:

ASPX MasterPage Copy Code
<rad:RadAjaxManager ID="RadAjaxManager1" runat="server" />
<asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server">
</asp:ContentPlaceHolder>
<asp:Panel ID="Panel1" runat="server">
 <asp:ContentPlaceHolder ID="ContentPlaceHolder2" runat="server">
 </asp:ContentPlaceHolder>
</asp:Panel>

This MasterPage has no code-behind.

 

Standard content page ASPX:

ASPX Content Page Copy Code
<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder2" runat="Server">
</asp:Content>

The key content page code-behind:

C# Content Page Copy Code
private object Content(string id)
{
return Page.Master.FindControl(id);
}
protected void Page_Load(object sender, System.EventArgs e)
{
//Load
Content("ContentPlaceHolder1").Controls.Add(LoadControl("~/Page1.ascx"));
Content("ContentPlaceHolder1").Controls(1).ID = "UserControl1";
//Get loaded user control's buttons
Button AjaxButtonLoad = (Button)Content("ContentPlaceHolder1").FindControl("UserControl1").FindControl("btnLoad");
Button AjaxButtonClear = (Button)Content("ContentPlaceHolder1").FindControl("UserControl1").FindControl("btnClear");
//Get the manager and the panel from the MasterPage
RadAjaxManager AjaxManager = (RadAjaxManager)Content("RadAjaxManager1");
Panel MyPanel = (Panel)Content("Panel1");
//Add the necessary AJAX settings - buttons update the panel in order to load the second user control there
AjaxManager.AjaxSettings.AddAjaxSetting(AjaxButtonLoad, MyPanel, null);
AjaxManager.AjaxSettings.AddAjaxSetting(AjaxButtonClear, MyPanel, null);
}
protected override bool OnBubbleEvent(object source, System.EventArgs args)
{
CommandEventArgs commandArgs = args as CommandEventArgs;
//determine whether to load the user control depending on bubbled button command
if (commandArgs != null)
{
 if (commandArgs.CommandName == "Load")
 {
  Content("ContentPlaceHolder2").Controls.Add(LoadControl("~/Page2.ascx"));
  Content("ContentPlaceHolder2").Controls(1).ID = "UserControl2";
 }
else if (commandArgs.CommandName == "Clear") {
  //do nothing. the control won't be loaded anyway
 }
}
return base.OnBubbleEvent(source, args);
}
VB.NET Content Page Copy Code
Private Function Content(ByVal id As String)
 Return Page.Master.FindControl(id)
End Function
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
 'Load
 Content("ContentPlaceHolder1").Controls.Add(LoadControl("~/Page1.ascx"))
 Content("ContentPlaceHolder1").Controls(1).ID = "UserControl1"
 'Get loaded user control's buttons
 Dim AjaxButtonLoad As Button = CType(Content("ContentPlaceHolder1").FindControl("UserControl1").FindControl("btnLoad"), Button)
 Dim AjaxButtonClear As Button = CType(Content("ContentPlaceHolder1").FindControl("UserControl1").FindControl("btnClear"), Button)
 'Get the manager and the panel from the MasterPage
 Dim AjaxManager As RadAjaxManager = CType(Content("RadAjaxManager1"), RadAjaxManager)
 Dim MyPanel As Panel = CType(Content("Panel1"), Panel)
 'Add the necessary AJAX settings - buttons update the panel in order to load the second user control there
 AjaxManager.AjaxSettings.AddAjaxSetting(AjaxButtonLoad, MyPanel, Nothing)
 AjaxManager.AjaxSettings.AddAjaxSetting(AjaxButtonClear, MyPanel, Nothing)
End Sub
Protected Overrides Function OnBubbleEvent(ByVal source As Object, ByVal args As System.EventArgs) As Boolean
 Dim commandArgs As CommandEventArgs = TryCast(args, CommandEventArgs)
 'determine whether to load the user control depending on bubbled button command
 If commandArgs IsNot Nothing Then
  If commandArgs.CommandName = "Load" Then
   Content("ContentPlaceHolder2").Controls.Add(LoadControl("~/Page2.ascx"))
   Content("ContentPlaceHolder2").Controls(1).ID = "UserControl2"
  ElseIf commandArgs.CommandName = "Clear" Then
   'do nothing. the control won't be loaded anyway
  End If
 End If
 Return MyBase.OnBubbleEvent(source, args)
End Function
First WebUserControl's code, which is loaded on each page load:
ASPX WebUserControl Copy Code
<asp:Button ID="btnLoad" runat="server" Text="Load" CommandName="Load" />
<asp:Button ID="btnClear" runat="server" Text="Clear" CommandName="Clear" />  

Code-behind:

C# WebUserControl Copy Code
public event EventHandler BtnClick;
protected void Button1_Click(object sender, System.EventArgs e)
{
if (BtnClick != null) {
 BtnClick(sender, e);
}
}
VB.NET WebUserControl Copy Code
Public Event BtnClick As EventHandler
Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnLoad.Click
 RaiseEvent BtnClick(sender, e)
End Sub

And the second WebUserControl, which is loaded when the "Load" button in the first WebUserControl is clicked:

It just shows some text in the ASPX:

UserControl2

and has no code-behind.