/// <summary>
/// 设置全屏或这取消全屏
/// </summary>
/// <param name="fullscreen">true:全屏 false:恢复</param>
/// <param name="rectOld">设置的时候，此参数返回原始尺寸，恢复时用此参数设置恢复</param>
/// <returns>设置结果</returns>
public static bool SetFullScreen(bool fullscreen, ref Rectangle rectOld)
{
    int Hwnd = 0;    
    Hwnd = FindWindow("Shell_TrayWnd", null);
    if (Hwnd == 0) return false;
    if (fullscreen)
    {
        ShowWindow(Hwnd, SW_HIDE);
        Rectangle rectFull = Screen.PrimaryScreen.Bounds;
        SystemParametersInfo(SPI_GETWORKAREA, 0, ref rectOld, SPIF_UPDATEINIFILE);//get
        SystemParametersInfo(SPI_SETWORKAREA, 0, ref rectFull, SPIF_UPDATEINIFILE);//set
    }
    else
    {
        ShowWindow(Hwnd, SW_SHOW);
        SystemParametersInfo(SPI_SETWORKAREA, 0, ref rectOld, SPIF_UPDATEINIFILE);
    }
    return true;
}

[DllImport("user32.dll", EntryPoint = "ShowWindow")]
public static extern int ShowWindow(int hwnd, int nCmdShow);
public const int SW_SHOW = 5;public const int SW_HIDE = 0;

[DllImport("user32.dll", EntryPoint = "SystemParametersInfo")]
private static extern int SystemParametersInfo(int uAction, int uParam, ref Rectangle lpvParam, int fuWinIni);
public const int SPIF_UPDATEINIFILE = 0x1;
public const int SPI_SETWORKAREA = 47;
public const int SPI_GETWORKAREA = 48;