Load user controls		Send comments on this topic.
See Also

How-to > Load user controls

Visual Basic .NET
C#

Glossary Item Box

The dynamic loading of user controls follows the same logic as in normal postback application with small specifics regarding the usage of either of the Telerik RadAjax controls. The only difference between the standard loading of controls and AJAX loading is that you should add the control in an asp:Panel instead of a Placeholder. This is due to the fact that the Placeholder does not render any HTML output and therefore cannot be updated with our ajax control. You can load custom user controls via AJAX requests by following the steps below:

You need to have an appropriate container for it - usually that will be a specially designated asp:panel.
Instantiate your user control in Page_Init or Page_Load and always recreate the last loaded User Control:

VB.NET Copy Code

Dim MyControl As UserControl = Me.LoadControl(controlName)
Me.LoadMyUserControl( Me.CurrentControl, Panel1)

C# Copy Code

UserControl MyControl = (UserControl)LoadControl(controlName);
LoadMyUserControl(CurrentControl, Panel1);
Make sure you assign unique ID to the dynamically loaded User Control:

VB.NET Copy Code

Dim userControlID As String = controlName.Split("."c)(0)
MyControl.ID = userControlID.Replace("/", "").Replace("~", "")

C# Copy Code

string userControlID = controlName.Split('.')[0];
MyControl.ID = userControlID.Replace("/", "").Replace("~", "");
Place the instance inside the controls collection of the container:

VB.NET Copy Code

parent.Controls.Add(MyControl)

C# Copy Code

parent.Controls.Add(MyControl);

Here is the code from a sample project:

ASPX/ASCX

Copy Code

And in the code-behind:

VB.NET

Copy Code

    Private Property LatestLoadedControlName() As String
        Get
            Return CStr(ViewState("LatestLoadedControlName"))
        End Get
        Set(ByVal value As String)
            ViewState("LatestLoadedControlName") = value
        End Set
    End Property
    Private Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If Not (LatestLoadedControlName Is Nothing) Then
            LoadUserControl(LatestLoadedControlName)
        Else
            LoadUserControl("WebUserControl1.ascx")
        End If
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        LoadUserControl("WebUserControl1.ascx")
    End Sub
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        LoadUserControl("WebUserControl2.ascx")
    End Sub
    Public Sub LoadUserControl(ByVal controlName As String)
        If Not (LatestLoadedControlName Is Nothing) Then
            Dim previousControl As Control = Panel1.FindControl(LatestLoadedControlName.Split("."c)(0))
            If Not (previousControl Is Nothing) Then
                Me.Panel1.Controls.Remove(previousControl)
            End If
        End If
        Dim userControlID As String = controlName.Split("."c)(0)
        Dim targetControl As Control = Panel1.FindControl(userControlID)
        If targetControl Is Nothing Then
            Dim userControl As UserControl = CType(Me.LoadControl(controlName), UserControl)
            'slashes and tildes are forbidden
            userControl.ID = userControlID.Replace("/", "").Replace("~", "")
            Me.Panel1.Controls.Add(userControl)
            LatestLoadedControlName = controlName
        End If
    End Sub

Copy Code

   private void Page_Load(object sender, System.EventArgs e)
   {
       if (LatestLoadedControlName != null)
       {
           LoadUserControl(LatestLoadedControlName);
       }
       else
       {
           LoadUserControl("WebUserControl2.ascx");
       }
   }
   protected void Button1_Click(object sender, EventArgs e)
   {
       LoadUserControl("WebUserControl1.ascx");
   }
   protected void Button2_Click(object sender, EventArgs e)
   {
       LoadUserControl("WebUserControl2.ascx");
   }

   public void LoadUserControl(string controlName)
   {
       if (LatestLoadedControlName != null)
       {
           Control previousControl = Panel1.FindControl(LatestLoadedControlName.Split('.')[0]);
           if (previousControl != null)
           {
               this.Panel1.Controls.Remove(previousControl);
           }
       }
       string userControlID = controlName.Split('.')[0];
       Control targetControl = Panel1.FindControl(userControlID);
       if (targetControl == null)
       {
           UserControl userControl = (UserControl)this.LoadControl(controlName);
           //slashes and tildes are forbidden
           userControl.ID = userControlID.Replace("/", "").Replace("~", "");
           this.Panel1.Controls.Add(userControl);
           LatestLoadedControlName = controlName;
       }
   }
   private string LatestLoadedControlName
   {
       get
       {
           return (string)ViewState["LatestLoadedControlName"];
       }
       set
       {
           ViewState["LatestLoadedControlName"] = value;
       }
   }

For full code working application you can check this example in Telerik RadAjax Quick Start Framework:

http://www.telerik.com/demos/aspnet/Ajax/Examples/Common/LoadingUserControls/DefaultCS.aspx

RadAjax for ASP.NET

See Also