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Error when mixing RadAjaxManager and asp:UpdatePanel using asp:PostBackTrigger

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Zoe asked on 06 Jun 2008, 11:42 AM

Hi,

We have a large web application project which we want to start implementing RadAjaxManager in, due to advantages it has over standard UpdatePanels. Unfortunately we have come across a problem which prevents gradual integration, which is that if the RadAjaxManager is set to update a usercontrol (or a control containing the usercontrol) which itself contains a normal asp UpdatePanel with a PostBackTrigger defined (as opposed to the usual AsyncPostBackTrigger) then you get an error when loading the page Unable to cast object of type 'System.Web.UI.PostBackTrigger' to type 'System.Web.UI.AsyncPostBackTrigger'. It looks like something in the RadAjaxManager might be assuming that all triggers are of the latter type?

I have replicated this problem in a small project (with very contrived examples but they show the error). We can work around the error now we know what the cause is, but it does mean updating quite a lot of pages/controls where PostBackTrigger is already used, whereas we had hoped to avoid a mass change all at once. The application is very large and quite complex so we may just abandon using RadAjaxManager for now, which would be a shame.

I'm posting this because the error message was not found by google (frustrating - if anyone else happens to encounter this they'll hopefully find this post now) and there's a chance someone might have a bright idea or tell me the obvious thing that's wrong, or Telerik might fix it/document it :)

Controls/UpdatePanelControl.ascx snippet

    
            <asp:UpdatePanel ID="UpdatePanel1" runat="server" ChildrenAsTriggers="False" UpdateMode="Conditional"> 
        
                <ContentTemplate> 
        
                    <div class="count"> 
        
                        <asp:Label ID="lblCount" runat="server" Text="0"></asp:Label> 
        
                        <asp:Button ID="btnAdd" runat="server" OnClick="btnAdd_Click" Text="Add" /> 
        
                    </div> 
        
                </ContentTemplate> 
        
                <Triggers> 
        
                    <asp:PostBackTrigger ControlID="btnAdd" /> 
        
                </Triggers> 
        
            </asp:UpdatePanel>

Controls/UpdatePanelControl.ascx.cs click event handler

    
                    protected void btnAdd_Click(object sender, EventArgs e) 
        
                    { 
        
                        int count; 
        
                        if (!int.TryParse(lblCount.Text, out count)) 
        
                            count = 1; 
        
                        lblCount.Text = (count + 1).ToString(); 
        
                    }

RADAjaxManagerError.aspx snippet

    
                    <telerik:RadScriptManager ID="ScriptManagerRad" runat="server"></telerik:RadScriptManager> 
        
                    <h1>Header that should be static</h1> 
        
                    <asp:Button ID="btnPanel" runat="server" Text="Hide Panel" onclick="btnPanel_Click" /> 
        
                    <asp:Panel ID="pnlShowHide" runat="server"> 
        
                        <ctl:updatepanelcontrol runat="server" ID="ctlUpdate" /> 
        
                    </asp:Panel> 
        
                    <telerik:RadAjaxManager ID="RadAjaxManager1" runat="server"> 
        
                        <AjaxSettings> 
        
                            <telerik:AjaxSetting AjaxControlID="btnPanel"> 
        
                                <UpdatedControls> 
        
                                    <telerik:AjaxUpdatedControl ControlID="btnPanel" /> 
        
                                    <telerik:AjaxUpdatedControl ControlID="pnlShowHide" /> 
        
                                </UpdatedControls> 
        
                            </telerik:AjaxSetting> 
        
                        </AjaxSettings> 
        
                    </telerik:RadAjaxManager>

RADAjaxManagerError.aspx.cs click event handler

    
                    protected void btnPanel_Click(object sender, EventArgs e) 
        
                    { 
        
                        btnPanel.Text = btnPanel.Text == "Hide Panel" ? "Show Panel" : "Hide Panel"; 
        
                        pnlShowHide.Visible = !pnlShowHide.Visible; 
        
                    }

11 Answers, 1 is accepted

answered on 12 Jun 2008, 08:04 PM

I'm also experiencing this problem. The problem with the workaround which Pavel suggested is that the RadAjaxManager does not allow you to specify that a specific control should cause a real post back rather than an ajax request. We need a certain button to cause a real post back because our form contains a RadUpload control, and files cannot be uploaded using an ajax request.

Workarounds are suggested in the RadUpload documentation, but they are undesirable in that they require the use of javascript, which we have not used in any other place on our site, and with which I am not familiar.

I submitted a RadGrid bug a few days ago with a very similiar exception (see support ticket 140452). The Telerik representation said that the problem was related to LINQ. May I suggest that this problem may be LINQ related as well?