Change mp3 playback volume via wmplib in c #

The idea is to send a WM_APPCOMMAND message (also see this answer ),

For WPF, use WindowInteropHelper to get Handle

Window

:

class MainWindow : Window
{
    ...

    private const int APPCOMMAND_VOLUME_MUTE = 0x80000;
    private const int WM_APPCOMMAND = 0x319;
    private const int APPCOMMAND_VOLUME_UP = 10 * 65536;
    private const int APPCOMMAND_VOLUME_DOWN = 9 * 65536;

    [DllImport("user32.dll")]
    public static extern IntPtr SendMessageW(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);

    private void VolumeUp()
    {
        // APPCOMMAND_VOLUME_UP or APPCOMMAND_VOLUME_DOWN
        var windowInteropHelper = new WindowInteropHelper(this);
        SendMessageW(windowInteropHelper.Handle, (IntPtr)WM_APPCOMMAND, windowInteropHelper.Handle, (IntPtr)APPCOMMAND_VOLUME_UP);
    }
}

      

        
        
        
      

    

For Windows Forms use the Control.Handle Property :

class MainForm : Form
{
    ...

    private void VolumeUp()
    {
        SendMessageW(Handle, (IntPtr)WM_APPCOMMAND, Handle, (IntPtr)APPCOMMAND_VOLUME_UP);
    }
}