MediaControl/Program.cs

using System;
using Windows.Media.Control;
using WindowsMediaController;

namespace MediaControl
{
    class Program
    {
        static void Main(string[] args)
        {
            // We expect one argument: playpause, next, or previous
            if (args.Length == 0)
            {
                Console.WriteLine("Usage: MediaControl.exe <playpause|next|previous>");
                return;
            }

            var command = args[0].ToLowerInvariant();

            using (var mediaManager = new MediaManager())
            {
                mediaManager.Start();

                // MediaManager.CurrentMediaSessions is a Dictionary<string, MediaSession>
                var sessions = mediaManager.CurrentMediaSessions;
                foreach (var sessionKvp in sessions)
                {
                    var session = sessionKvp.Value;
                    
                    // Filter so only sessions with "spotify" in the Id get commands
                    // You might need to do a more exact match depending on the session's actual Id:
                    // e.g., if (session.Id?.Equals("Spotify.exe", StringComparison.OrdinalIgnoreCase) == true)
                    if (!session.Id?.ToLower().Contains("spotify") == true)
                        continue;  // skip non-Spotify sessions

                    var controlSession = session.ControlSession;
                    if (controlSession == null) 
                        continue;

                    switch (command)
                    {
                        case "playpause":
                            controlSession.TryTogglePlayPauseAsync();
                            break;
                        case "next":
                            controlSession.TrySkipNextAsync();
                            break;
                        case "previous":
                            controlSession.TrySkipPreviousAsync();
                            break;
                    }
                }
            }
        }
    }
}