Hi,

You can find an example here:
http://mindfusion.eu/Forum/YaBB.pl?num=1337156437/1#1

KeyDown should work too, but to make sure the keyboard focus isn't captured by ScrollViewer, set <ScrollViewer Focusable="False" ... >

I hope that helps,
Stoyan

Arrow keys will unselect a node to select adjacent one if you leave the default Diagram.Navigate* bindings shown in sample linked above and try to handle via other commands or KeyDown handler. They won't execute if you handle PreviewKeyDown though, so you can process both arrow and shift+arrow key from such PreviewKeyDown handler:

private void OnDiagramKeyDown(object sender, KeyEventArgs e)
{
	var node = diagram.ActiveItem as DiagramNode;
	if (node == null)
		return;

	int amount = (Keyboard.Modifiers & ModifierKeys.Shift) != 0 ?
		2 : 20;

	int dx = 0;
	int dy = 0;

	if (e.Key == Key.Left)
		dx = -amount;
	else if (e.Key == Key.Right)
		dx = +amount;
	else if (e.Key == Key.Up)
		dy = -amount;
	else if (e.Key == Key.Down)
		dy = +amount;
	else
		return;

	var r = node.Bounds;
	r.Offset(dx, dy);
	node.Bounds = r;

	e.Handled = true;
} 

It should be possible to set this up via command bindings too, but it seems the ScrollViewer has its own command bindings for shift+arrow keys with higher-priority that prevents them from reaching to diagram. So if you want to use commands instead of PreviewKeyDown, you'd have to find and remove shift+arrow bindings from ScrollViewer's InputBindings first.

I hope that helps,
Stoyan