premere C # Simula VolumeMute

Question

ho ottenuto il seguente codice per simulare volumemute pressione del tasto:

    [DllImport("coredll.dll", SetLastError = true)]
    static extern void keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo);

    byte VK_VOLUME_MUTE = 0xAD;
    const int KEYEVENTF_KEYUP = 0x2;
    const int KEYEVENTF_KEYDOWN = 0x0;
    private void button1_Click(object sender, EventArgs e)
    {
            keybd_event(VK_VOLUME_MUTE, 0, KEYEVENTF_KEYDOWN, 0);
            keybd_event(VK_VOLUME_MUTE, 0, KEYEVENTF_KEYUP, 0);
    }

Questo codice non funziona. So che c'è un altro modo per mute / disattivare l'audio da SendMessageW, ma io non voglio usare SendMessageW perché io uso KeyState per rilevare wheter ho bisogno di disattivare l'audio o riattivare il suono (se l'utente vuole riattivare il suono e la sua già riattivato allora io non bisogno di ginocchiera - ecco perché ho bisogno di simulare VolumeMute pressione di un tasto)

Grazie.

Answer 1

The first reason it doesn't work is because you use the wrong DLL, coredll.dll is Windows Mobile. In the desktop version of Windows, keybd_event is exported by user32.dll. The second reason it doesn't work is because sending the keystroke isn't good enough. Not quite sure why, this seems to be intercepted before the generic input handler.

You can use WM_APPCOMMAND, it supports a range of commands and APPCOMMAND_VOLUME_MUTE is one of them. It acts as a toggle, turning muting on and off. Make your code look like this:

    private void button1_Click(object sender, EventArgs e) {
        var msg = new Message();
        msg.HWnd = this.Handle;
        msg.Msg = 0x319;              // WM_APPCOMMAND
        msg.WParam = this.Handle;
        msg.LParam = (IntPtr)0x80000; // APPCOMMAND_VOLUME_MUTE
        this.DefWndProc(ref msg);
    }

This code needs to be inside a instance method of the form, note how it uses DefWndProc(). If you want to put it elsewhere then you need to fallback to SendMessage(). The actual window handle doesn't matter, as long as it is a valid toplevel one.