Code

private void OnMoveSelection(object sender, RoutedEventArgs e)
{
	var dx = 10;
	var dy = 0;

	diagram.StartCompositeOperation();

	foreach (var link in diagram.Selection.Links)
	{
		for (int i = 0; i < link.ControlPoints.Count; i++)
		{
			var linkCmd = new ChangeItemCommand(diagram, link);
			var point = link.ControlPoints[i];
			point.X += dx;
			point.Y += dy;
			link.ControlPoints[i] = point;
			diagram.ExecuteCommand(linkCmd);
		}
	}

	foreach (var node in diagram.Selection.Nodes)
	{
		var nodeCmd = new ChangeItemCommand(diagram, node);
		var bounds = node.Bounds;
		bounds.X += dx;
		bounds.Y += dy;
		node.Bounds = bounds;
		diagram.ExecuteCommand(nodeCmd);
	}

	diagram.CommitCompositeOperation();
}