FocusVolumeControlPlugin/src/FocusVolumeControl/AudioHelper.cs

using CoreAudio;
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace FocusVolumeControl
{
    internal class AudioHelper
    {
        ActiveAudioSessionWrapper GetSessionForProcess(Process process)
        {
            var deviceEnumerator = new MMDeviceEnumerator(Guid.NewGuid());

            using var device = deviceEnumerator.GetDefaultAudioEndpoint(DataFlow.Render, Role.Multimedia);
            using var manager = device.AudioSessionManager2;

            var sessions = manager.Sessions;

            foreach (var session in sessions)
            {
                var audioProcess = Process.GetProcessById((int)session.ProcessID);

                if (session.ProcessID == process.Id || audioProcess?.ProcessName == process.ProcessName)
                {
                    var displayName = audioProcess.MainModule.FileVersionInfo.FileDescription;
                    var path = audioProcess.MainModule.FileName;
                    return new ActiveAudioSessionWrapper()
                    {
                        DisplayName = displayName,
                        ExecutablePath = path,
                        Volume = session.SimpleAudioVolume
                    };
                }
            }
            return null;
        }

        internal ActiveAudioSessionWrapper GetActiveSession()
        {
            const int nChars = 256;
            IntPtr handle = IntPtr.Zero;
            StringBuilder Buff = new StringBuilder(nChars);
            handle = Native.GetForegroundWindow();

            if (handle == IntPtr.Zero)
            {
                //todo: return system or something like that?
                return null;
            }

            var tid = Native.GetWindowThreadProcessId(handle, out var pid);
            var process = Process.GetProcessById(pid);

            return GetSessionForProcess(process);
        }


    }
}