c#中多荧幕环境下，如何指定荧幕显示画面

private void ChangScreen(Form aform，int screenId)
{
    //先将form设为normal
    aform.WindowState = FormWindowState.Normal;

    //修改location
    aform.StartPosition = FormStartPosition.Manual;
    if (screenId < Screen.AllScreens.Length)
    {
        aform.Location =Screen.AllScreens[screenId].WorkingArea.Location;
    }
    //最大
    aform.WindowState = FormWindowState.Maximized;
}