public void OnMove(object o, MouseEventArgs e)
{
    if (e.LeftButton == MouseButtonState.Pressed)
    {
        b = (Button)o;
        SetZ();
        Canvas.SetZIndex(b, 99);
        b.Margin = new Thickness(e.MouseDevice.GetPosition(null).X - b.Width / 2, e.MouseDevice.GetPosition(null).Y - b.Height/2, b.Margin.Right, b.Margin.Bottom);
    }
}

public void OnKey(object o, KeyEventArgs e)
{
    int delta = 20;
    b = (Button)o;
    SetZ();
    Canvas.SetZIndex(b, 99);
    switch (e.Key)
    {
        case Key.W:
            b.Margin = new Thickness(b.Margin.Left, b.Margin.Top - delta, b.Margin.Right, b.Margin.Bottom);
            break;
        case Key.S:
            b.Margin = new Thickness(b.Margin.Left, b.Margin.Top + delta, b.Margin.Right, b.Margin.Bottom);
            break;
        case Key.A:
            b.Margin = new Thickness(b.Margin.Left - delta, b.Margin.Top, b.Margin.Right, b.Margin.Bottom);
            break;
        case Key.D:
            b.Margin = new Thickness(b.Margin.Left + delta, b.Margin.Top, b.Margin.Right, b.Margin.Bottom);
            break;
        default:
            break;
    }
}