Start/Stop Your Music Player with your Headphones

using System;
using System.Windows.Forms;
using Microsoft.WindowsMobile.Status;
using System.Diagnostics;
using OpenNETCF.ToolHelp;
using System.Threading;
using System.Runtime.InteropServices;
using System.Reflection;



namespace AutoNitro
{
  static class Program
  {
    static SystemState bHPState;

    // Music application name and path. Change here if your music application is different
    const string MUSIC_APP_EXE_NAME = "Nitrogen.exe";
    const string MUSIC_APP_PROGRAM_FOLDER = "\\Program Files\\Nitrogen";

    public const Int32 NATIVE_ERROR_ALREADY_EXISTS = 183;

    // .NetCF does not export CreateMutex. We have to explicitly import it here
    [DllImport("coredll.dll", EntryPoint = "CreateMutex", SetLastError = true)]
    public static extern IntPtr CreateMutex(IntPtr lpMutexAttributes, bool InitialOwner, string MutexName);


    /*****************************************************************************************/
    /*****************************************************************************************/
    /*****************************************************************************************/
    [MTAThread]
    static void Main()
    {
      // The name of this application
      String sThisApp = Assembly.GetExecutingAssembly().GetName().Name + ".exe";

      // Check if an instance is already running by trying to create a mutex with a fixed name.
      // If mutex already exists, we assume that this is because another instance is running!
      IntPtr hMutex = CreateMutex(IntPtr.Zero, true, "AutoNitro");
      if (Marshal.GetLastWin32Error() == NATIVE_ERROR_ALREADY_EXISTS)
      {
        if (DialogResult.Yes == MessageBox.Show(sThisApp + " is already running. Do you want to close it?", 
                                                sThisApp, 
                                                MessageBoxButtons.YesNo, 
                                                MessageBoxIcon.Question, 
                                                MessageBoxDefaultButton.Button1))
        {
          // Kill 'em All!  
          ProcessEntry[] processes = OpenNETCF.ToolHelp.ProcessEntry.GetProcesses();
          foreach (OpenNETCF.ToolHelp.ProcessEntry process in processes)
          {
            if (String.Compare(process.ExeFile, sThisApp, StringComparison.InvariantCultureIgnoreCase) == 0)
            {
              process.Kill();
            }
          }
        }
        return;
      }

      // Register to be notified for any change to the HeadsetPreset property
      bHPState = new SystemState(SystemProperty.HeadsetPresent);
      bHPState.Changed += bState_Changed;
      
      // Probably better to implement a message loop here instead of sleeping and DoEvents
      while (true)
      {
        Application.DoEvents();
        Thread.Sleep(1000);
      }
    }

    /*****************************************************************************************/
    /*****************************************************************************************/
    /*****************************************************************************************/
    // Returns true if the application with the name passed as parameter is currently running
    static bool IsApplicationRunning(string pAppName)
    {
      ProcessEntry[] processes = OpenNETCF.ToolHelp.ProcessEntry.GetProcesses();
      foreach (OpenNETCF.ToolHelp.ProcessEntry process in processes)
      {
        if (String.Compare(process.ExeFile, pAppName, StringComparison.InvariantCultureIgnoreCase) == 0)
        {
          return true;
        }
      }
      return false;
    }

    /*****************************************************************************************/
    /*****************************************************************************************/
    /*****************************************************************************************/
    // Shutsdown all running instances of the application pAppName
    static void TerminateApplication(string pAppName)
    {
      ProcessEntry[] processes = OpenNETCF.ToolHelp.ProcessEntry.GetProcesses();
      foreach (OpenNETCF.ToolHelp.ProcessEntry process in processes)
      {
        if (String.Compare(process.ExeFile, pAppName, StringComparison.InvariantCultureIgnoreCase) == 0)
        {
          // We can directly kill the process here but it is not supposedly safe.
          // I don't prefer killing because the music app will not remember your last played
          // track and position if you kill it. Instead ask for a shutdown politely.
          Process p = System.Diagnostics.Process.GetProcessById((int)process.ProcessID);
          p.CloseMainWindow();
        }
      }
    }

    /*****************************************************************************************/
    /*****************************************************************************************/
    /*****************************************************************************************/
    private static void LaunchApplication(string pAppName)
    {
      System.Diagnostics.Process.Start(pAppName, "");
    }

    /*****************************************************************************************/
    /*****************************************************************************************/
    /*****************************************************************************************/
    static void bState_Changed(object sender, ChangeEventArgs args)
    {
      Boolean blNewHPState = Convert.ToBoolean(args.NewValue);
      bool blAppRunState = IsApplicationRunning(MUSIC_APP_EXE_NAME);

      if (!blNewHPState)
      {
        if (true == blAppRunState)
        {
          TerminateApplication(MUSIC_APP_EXE_NAME);
        }
      }
      else
      {
        if (false == blAppRunState)
        {
          string sApp = MUSIC_APP_PROGRAM_FOLDER + "\\" + MUSIC_APP_EXE_NAME;
          try
          {
            LaunchApplication(sApp);
          }
          catch
          {
            throw new Exception("Failed to start music player.\nPath was " + sApp);
          }
        }
      }
    }
  }
}