Drag Drop Sample with WPF

[Robert]

I'm working with the getting started article to demonstrate a basic implementation of the DragDropManager by dragging between two ListBoxes - http://www.telerik.com/help/wpf/dragdropmanager-getting-started.html ;

The following code produces an ArgumentException error - The value "System.Windows.DataObject" is not of type "ManageDragDrop.ApplicationInfo" and cannot be used in this generic collection.

private void OnDrop(object sender, Telerik.Windows.DragDrop.DragEventArgs args)
        {
            ((IList)(sender as ListBox).ItemsSource).Add(args.Data);
        }

[Dimitrina]

Hi Robert,

 Indeed you are right. 
You will need to change the OnDragInitialize and the OnDrop events like so:

private void OnDragInitialize(object sender, DragInitializeEventArgs args)
{
    args.AllowedEffects = DragDropEffects.All;
    args.Data = ((FrameworkElement)args.OriginalSource).DataContext;
    args.DragVisual = new ContentControl { Content = args.Data, ContentTemplate = LayoutRoot.Resources["ApplicationTemplate"] as DataTemplate };
}

private void OnDrop(object sender, Telerik.Windows.DragDrop.DragEventArgs args)
{
    ((IList)(sender as ListBox).ItemsSource).Add(((DataObject)args.Data).GetData(typeof(ApplicationInfo)));
}

Thank you for this remark. The help article will be updated and uploaded to live until the end of the week.

Regards,
Didie
the Telerik team

[Ahmet]

I know this is a fairly simple example, and I have followed the demo, but still cannot get it working.

Can someone please, please, please post a working solution of this example? (in VB, if possible)

Thanks.

[James]

I have the same problem. The VB.Net code for the getting started article is all jacked up. I was able to fix the typos but still can't get the demo to run. When I try to drag from the list nothing happens and OnDragInitialized never fires. I assume I'm missing some key piece of information. 

[Nick]

Hi James,

You need to do a couple of things to ensure the firing of the events. The draggable element, in that case, the ListBoxItem, has to have the DragDropManager.AllowDrag/AllowCapturedDrag property set to true. 
If anything else is handling the DragInitialize event, such as a DragDropBehavior, you need to subscribe to it with HandledEventsToo set to true.

Let me know if this helps! 

Regards,
Nik
Telerik