Send multimedia commands

Question

Is there some way that I can send multimedia control commands like next song, pause, play, vol up, etc. to the operating system? Commands that are sent when pressing Fn

Answer 1

_{Actually, the answer of dxramax gives me erratic behavior. I'm posting this answer that gives me consistent behavior, and also has some more details.}

To send multimedia keys, including Play/Pause, NextTrack, PrevTrack, etc, you can use keybd_event:

public class Program
{
    public const int KEYEVENTF_EXTENTEDKEY = 1;
    public const int KEYEVENTF_KEYUP = 0;
    public const int VK_MEDIA_NEXT_TRACK = 0xB0;
    public const int VK_MEDIA_PLAY_PAUSE = 0xB3;
    public const int VK_MEDIA_PREV_TRACK = 0xB1;

    [DllImport("user32.dll")]
    public static extern void keybd_event(byte virtualKey, byte scanCode, uint flags, IntPtr extraInfo);

    public static void Main(string[] args)
    {
        keybd_event(VK_MEDIA_PLAY_PAUSE, 0, KEYEVENTF_EXTENTEDKEY, IntPtr.Zero);    // Play/Pause

        //keybd_event(VK_MEDIA_PREV_TRACK, 0, KEYEVENTF_EXTENTEDKEY, IntPtr.Zero);  // PrevTrack
        //keybd_event(VK_MEDIA_NEXT_TRACK, 0, KEYEVENTF_EXTENTEDKEY, IntPtr.Zero);  // NextTrack
    }

Here is a list to the supported key codes that this windows api can handle:
https://docs.microsoft.com/en-us/windows/win32/inputdev/virtual-key-codes

The SendKeys class is very nice, but it's also limited. The approach above sends the key command directly to Windows OS.

Answer 2

Unfortunately, in most cases, keys Fn can't be sent using Windows API and as a result - using .NET classes. It depends on how the manufacturer has done this functionality. Probably it is supported by additional driver or even go over operation system.

You can check if it's possible to send Fn commands from the code by trying to hook them using Windows API code or some application like AutoHotKey. For instance, on my laptop, I can't hook multimedia commands.

Otherwise, if you are lucky, use SendKeys as mentioned in the comments.

Answer 3

You can use keybd_event to simulate keys presses, you have to simulate key down and then key up in order to recognize correctly

    [DllImport("user32.dll", SetLastError = true)]
    public static extern void keybd_event(byte virtualKey, byte scanCode, uint flags, IntPtr extraInfo);
    public const int VK_MEDIA_NEXT_TRACK = 0xB0;
    public const int VK_MEDIA_PLAY_PAUSE = 0xB3;
    public const int VK_MEDIA_PREV_TRACK = 0xB1;
    public const int KEYEVENTF_EXTENDEDKEY = 0x0001; //Key down flag
    public const int KEYEVENTF_KEYUP = 0x0002; //Key up flag

    private void ButtonClick(object sender, EventArgs e)
        keybd_event(VK_MEDIA_PREV_TRACK, 0, KEYEVENTF_EXTENDEDKEY, IntPtr.Zero);
        keybd_event(VK_MEDIA_PREV_TRACK, 0, KEYEVENTF_KEYUP, IntPtr.Zero);
    }`