[Solved] 500 error when using custom template

[Matt Travis]

Hello,

I'm getting the following javascript Ajax related error when I set up a custom iTemplate instead of using the Telerik GridTemplateColumn.  The error shows up when I click on the custom link I create instead of using the aspx GridTemplateColumn's link.

Sys.WebForms.PageRequestManagerServerErrorException: Object reference not set to an instance of an object.

The error details say it is a 500 error.

If I use the GridTemplateColumn shown below, it works fine.

<Columns>
     <telerik:GridTemplateColumn UniqueName="Delete" AllowFiltering='false'>
          <HeaderStyle Width="45px" />
          <ItemStyle CssClass="c" />
          <ItemTemplate>
               <asp:HyperLink ID="DeleteLink" runat="server" Text="Delete" />
          </ItemTemplate>
     </telerik:GridTemplateColumn>
</Columns>

But when I convert it to an iTemplate using the following code, I receive the error.

Dim type As String = "Delete"
Dim column As New GridTemplateColumn
column.AllowFiltering = False
column.HeaderStyle.Width = 45
column.ItemStyle.CssClass = "c"
column.ItemTemplate = New HyperlinkTemplate(type)
column.UniqueName = type
RadGrid1.MasterTableView.Columns.Add(column)

My HyperlinkTemplate is the following class.

Public Class HyperlinkTemplate
    Implements ITemplate
    Private _type As Object

    Public Sub New(ByVal type As String)
        MyBase.New()
        _type = type
    End Sub

    Public Sub InstantiateIn(ByVal container As Control) Implements ITemplate.InstantiateIn
        Dim hl As New HyperLink
        hl.EnableViewState = False
        hl.ID = _type & "Link"
        hl.Text = _type
        hl.Attributes("href") = "#"
        container.Controls.Add(hl)
    End Sub
End Class

I have an OnItemCreated event that runs the following code which adds an onclick event which I will show next and customizes the ID to make it unique:

Dim deleteLink As HyperLink = DirectCast(e.Item.FindControl("DeleteLink"), HyperLink)
deleteLink.Attributes("onclick") = [String].Format("return Delete('{0}');", e.Item.OwnerTableView.DataKeyValues(e.Item.ItemIndex)(IDcolumnIsHere))
deleteLink.ID &= e.Item.ItemIndex

The onclick code calls the RadAjaxManager I have set up.

function Delete(id) { $find("<%= RadAjaxManager1.ClientID %>").ajaxRequest("Grid,Delete," + customValue + "," + id); }

The custom column is added during the Page_Load event.

It never reaches the Ajax Handler I have set up unless I use the aspx GridTemplateColumn instead of my custom template.

Am I doing something wrong with the iTemplate or am I not initializing something I should be that integrates it with the RadGrid?  I've tried going through the various properties available to me for the column and the iTemplate, but I haven't had any luck making the error go away so I know I'm missing something... just not sure what.

[Rosen]

Hello Matt Travis,

Can you please try to disable the ajax functionality, as this way you will be able to see the full stacktrace of the exception and locate more precisely where it has occurred.

Sincerely yours,
Rosen
the Telerik team

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[Matt Travis]

I changed the Ajax request to a postback, and it turns out that it is dieing because the Hyperlink Template isn't added to the grid before the logic attempts to set the link for it (i.e. the ItemCreated event is firing before the Page Load event).

I'm in the process of adding a work around that involves storing the related IDs during the Item Creation Event, but if you can recommend an event that works similar to ItemCreated (gives me access to each grid item row and their child controls) but is handled after the load, it might save me some time.

[Matt Travis]

I've completed my work around so I don't need the event any more.  Marking the initial reply you left as the answer.

[Ivan Stoilkov]

Thank you Rosen! Your simple suggestion helped me to locate the root of the server error in my case. I am using a rad grid control to populate data from a database and a user web control to edit/create the data on the grid. In my case the exception was not being raised on my development environment, it also was updating the data, but on the test server it gave me the server error message. Disabling the ajax functionality of the grid showed me the error on the stack trace. I was implicitly converting a rad textbox to an asp textbox and the server did not like that. However, the IDE of VS 2008 allowed the implicit conversion of the two types, which did not raise the excepton on the dev.
But, this is a very good startup point: to temporarily disable the ajax functionality