使用Windows消息按住Alt按钮

如何在窗口消息中按住ALT按钮？

有WM_KEYHOLD或类似的东西吗？

这是屏幕截图的代码，但我想有什么遗漏了。我认为我使用的密钥代码不好，对于0x70，它发送F1。而对于0x46，它发送一个不正常的窗口声音。

    const uint WM_SYSKEYDOWN = 260;
    const uint VK_MENU = 18;//virtual key code of Alt key
    const uint VK_SNAPSHOT = 44;//virtual key code of Snapshot key
    [DllImport("User32.Dll")]
    public static extern long PostMessage(IntPtr hWnd, UInt32 wMsg, long wParam, long lParam);
    [DllImport("user32.dll")]
    public static extern IntPtr FindWindow(String sClassName, String sAppName);
    [DllImport("user32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]
    public static extern IntPtr GetForegroundWindow();
    private void timer1_Tick(object sender, EventArgs e)
    {
        IntPtr hwnd = GetForegroundWindow();
        //PostMessage(hwnd, WM_SYSKEYDOWN, VK_MENU, 1);
        PostMessage(hwnd, WM_SYSKEYDOWN, VK_SNAPSHOT, 1);
    }