Error: “This operation is valid only on elements that have this template applied”

[Jeff]

I have a C# WPF application that contains a user control:

<UserControl
        x:Name="payrollEntryControl"
        x:Class="MyNamespace.PayrollEntryControl"
        [...]
        >
    [...]
</UserControl>

Within the user control, I have a Telerik RadDataForm:

<telerik:RadDataForm
        x:Name="payrollAddForm"
        CurrentItem="[...]"
        EditTemplate="{StaticResource myEditTemplate}"
        />

 

The template contains a Telerik RadGridView and a Button:

<telerik:RadGridView Grid.Row="0" Grid.Column="0"
        x:Name="workGridView"
        [...]
        ItemsSource="{Binding [...]}"
        >
    <telerik:RadGridView.Columns>
        [...]
    </telerik:RadGridView.Columns>
</telerik:RadGridView>
<Button Grid.Row="1" Grid.Column="0"
        Command="{Binding addWorkCommand, ElementName=payrollEntryControl}"
        >
    Add
</Button>

I want the command to do is call BeginInsert() on workGridView. But I can't seem to get access to workGridView.

My command, so far:

private DelegateCommand addWorkCommand_ = null;
public DelegateCommand addWorkCommand
{
    get
    {
        if (this.addWorkCommand_ == null)
        {
            this.addWorkCommand_ = new DelegateCommand(
                o => addWork(o)
            );
        }

        return this.addWorkCommand_;
    }
}

private void addWork(object o)
{
    var addForm = this.payrollAddForm;
    var editTemplate = addForm.EditTemplate;
    var workGrid = editTemplate.FindName("workGridView", addForm);
}

 

My problem? When I make the call to editTemplate.FindName(), I get an exception:

This operation is valid only on elements that have this template applied.

I don't understand. I'm getting the template from the form. How can it not be applied?

[Jeff]

Any ideas? I'm still stuck.

[Stefan Nenchev]

Hi Jeff,

I suggest you pass the workGridView as a CommandParameter and eventually use the RadGridView BeginInsert method:

<Button Grid.Row="1" Grid.Column="0"
        CommandParameter="{Binding ElementName=workGridView}"
        Command="{Binding addWorkCommand}" >

....

  private void addWork(object o)
        {
            RadGridView grid = o as RadGridView;
            grid.BeginInsert();
        }

Would this work for you?

Regards,
Stefan Nenchev
Telerik by Progress

[Jeff]

It very well might.

I'd found a hack using VisualTreeHelper that seems to work, but I'm not really comfortable with it.

Thanks.

[Stefan Nenchev]

Hello Jeff,

I have tested the suggested approach with the CommandParameter and it works as expected. Please give it a try as it seems appropriate for your scenario.

Regards,
Stefan Nenchev
Telerik by Progress

[Jeff]

Thank you.