Ok now that I change it for your uri namespace telerik, it works. I've send a comment to the documentation team
I've implemented the article as is and when I move the cue on the drop container which is a StackPanel instead of a ListBox, every pixel I move over the Stack Panel it's changing the cue to not possible and possible very rapidelly for every pixel I move so I have to be at the right pixel to have the cue letting me drop the item and once I've dropped with difficulties, it gets twice in the DropInfo and I have twice the row from the grid in the destination container. What's wrong ? I can send a Repro so do I have to create a ticket for that ?