如何在Form中使用方向键

const int WM_SYSKEYDOWN=260;
const int WM_KEYDOWN=256;

protected override bool ProcessCmdKey(ref Message msg,Keys keyData)
{
if ((msg.Msg==WM_KEYDOWN)||(msg.Msg==WM_SYSKEYDOWN))
{
switch (keyData)
{
case Keys.Up:
MessageBox.Show("up");
break;
case Keys.Down:
MessageBox.Show("down");
break;
case Keys.Left:
MessageBox.Show("left");
break;
case Keys.Right:
MessageBox.Show("right");
break;
}
}
return true;
}