I have a DragCanvas class that inherits from Canvas and that implements functionality in order to grab, drag and resize elements. The DragCanvas class is very similar to the one
Set Focusable="True" for your canvas, then put this snippet into your window class and set DragCanvas into focus. Hope this helps you.
Focusable="True"
DragCanvas
Loaded += (x,y) => Keyboard.Focus(DragCanvas);