this.get_tree() is null

[Ed]

I have an existing site and Im starting to use telerik controls in the site but Im getting this javascript error.

this.get_tree() is null


Im using an existing ajaxControlToolkit.TabContainers. 

1. On the first tab you click a button and it displays a third tab containing a RadFileExplorer 
2. now you click on the first tab the 3rd tab goes away
3. then click on the second tab and the javascript error occurs.

This is some sample code to reproduce it (VB.net 4.0)

Protected Sub tabContainer1_ActiveTabChanged(sender As Object, e As System.EventArgs)
    If (tabContainer1.ActiveTabIndex = 0 Or tabContainer1.ActiveTabIndex = 1) Then
        With tabContainer1.Tabs(2)
            .Enabled = False
            .Visible = False
        End With
    End If
End Sub

Protected Sub Page_Load(sender As Object, e As System.EventArgs)
    If Not IsPostBack Then
        With tabContainer1.Tabs(2)
            .Enabled = False
            .Visible = False
        End With
    End If
End Sub

Protected Sub OpenNewTab_Click(sender As Object, e As System.EventArgs)
    With tabContainer1.Tabs(2)
        .Enabled = True
        .Visible = True
    End With
    tabContainer1.ActiveTab = tabContainer1.Tabs(2)
End Sub

<form id="form1" runat="server">
    <telerik:RadScriptManager ID="RadScriptManager1" ScriptMode="Release" AsyncPostBackTimeout="60000" runat="server">
    <Scripts>
        <asp:ScriptReference Assembly="Telerik.Web.UI" Name="Telerik.Web.UI.Common.Core.js" />
    </Scripts>
</telerik:RadScriptManager>
<telerik:RadAjaxManager ID="RadAjaxManager1" runat="server"></telerik:RadAjaxManager>
 <div>
     <asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>
    <ajaxControlToolKit:TabContainer ID="tabContainer1"  runat="server"
                ActiveTabIndex="0" AutoPostBack="True"
                     onactivetabchanged="tabContainer1_ActiveTabChanged">
        <ajaxControlToolKit:TabPanel ID="Tab1" runat="server">
            <HeaderTemplate>
                One
            </HeaderTemplate>
            <ContentTemplate>
            Randon <br />Stuff
            <br />Click here to start>><asp:Button runat="server" ID="OpenNewTab" Text="OpenNewTab"
                    onclick="OpenNewTab_Click" />
            </ContentTemplate>
        </ajaxControlToolKit:TabPanel>
        <ajaxControlToolKit:TabPanel ID="Tab2" runat="server">
            <HeaderTemplate>
                Two
            </HeaderTemplate>
            <ContentTemplate>
            More Random Stuff<br /><br />11111111
            </ContentTemplate>
        </ajaxControlToolKit:TabPanel>
        <ajaxControlToolKit:TabPanel ID="Tab3" runat="server">
            <HeaderTemplate>
                Three
            </HeaderTemplate>
            <ContentTemplate>
            problem here<br />

            <telerik:RadFileExplorer runat="server" ID="editArticleImagePathEditor" ></telerik:RadFileExplorer>
            </ContentTemplate>
        </ajaxControlToolKit:TabPanel>
    </ajaxControlToolKit:TabContainer>

        </ContentTemplate>
</asp:UpdatePanel>

</div>
</form>

[Dobromir]

Hi Edmond,

I tried to reproduce the reported problem but to no avail. Could you please provide more detailed information on the specific scenario?

• Which version of RadControls for ASP.NET AJAX, AjaxControlToolkit and .NET Framework are used in the application?
• Under which browser and its version the problem occurs?

Also, I have prepared a video demonstrating my test, could you please see if I am doing something wrong?
http://screencast.com/t/OpYEe8MCR 

For my test, I used the latest version of RadControls for ASP.NET AJAX Q1 2012 and the latest version of AjaxControlToolkit 4.1.51116.

Regards,
Dobromir
the Telerik team

[Ed]

Thanks for the quick reply. Im using AjaxControlToolKit 4.1.50508.0,Telerik 2011.3.1305.40. I get the error in Chrome and IE9 and 

[Dobromir]

Hi Edmond,

The provided screenshot does not say much about the JavaScript error. Also, the version of both suites are not latest. Could you please upgrade them and see if the problem still exists?

Kind regards,
Dobromir
the Telerik team