How to Run specific part of codes in Program Main just once in C#?

Question

I registered my application on ".mp3" Files.

My App is a Single Instance Application.

Goal: when user open a mp3 file if myApp isn't running Is start running and show the selected files count in explorer else show the app window and show the selected files count in explorer (Just Once). Then Call a function in application form that add the mylist items to listbox1.

2nd Problem: the results I get when call mylist in application form is different than the results in myfunc() why it's different?

I added commented lines thought may help!

I think my Question is clear! if it's not tell me to make it clear.

[STAThread]
    static void Main(string[] args)
    {
        if (SingleApplicationDetector.IsRunning())
        {// These Codes Runs n times!

            myfunc(); // But I want this Code Run just one time!

            return;
        }
        //myfunc();
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new MainForm());

        SingleApplicationDetector.Close();
    }

---

 public static class SingleApplicationDetector
{
    public static bool IsRunning()
    {
        string guid = ((GuidAttribute)Assembly.GetExecutingAssembly().GetCustomAttributes(typeof(GuidAttribute), false).GetValue(0)).Value.ToString();
        var semaphoreName = @"Global\" + guid;
        try
        {
            __semaphore = Semaphore.OpenExisting(semaphoreName, SemaphoreRights.Synchronize);

            Close();
            return true;
        }
        catch (Exception ex)
        {
            __semaphore = new Semaphore(0, 1, semaphoreName);
            return false;
        }
    }

    public static void Close()
    {
        if (__semaphore != null)
        {
            __semaphore.Close();
            __semaphore = null;
        }
    }

    private static Semaphore __semaphore;
}

---

 public static List<string> mylist = new List<string>();
    public static System.Diagnostics.Process[] p = System.Diagnostics.Process.GetProcessesByName("ACE Music Player");
    [DllImport("user32.dll")]
    static extern bool SetForegroundWindow(IntPtr hWnd);

    public static void myfunc()
    {

        if (!File.Exists("1.txt")) // I somehow achieved my goal by using this but it does not work very well for large number of files, and of course there should be a better solution!
        {
            File.WriteAllText("1.txt", "testing");
            if (p.Length > 0)
            {
                for (int i = 0; i < p.Length; i++)
                {
                    SetForegroundWindow(p[i].MainWindowHandle);
                }
            }
           // MessageBox.Show("Running");
            {
                try
                {

                    string filename;
                    List<string> selected = new List<string>();
                    foreach (SHDocVw.InternetExplorer window in new SHDocVw.ShellWindows())
                    {
                        filename = Path.GetFileNameWithoutExtension(window.FullName).ToLower();
                        if (filename.ToLowerInvariant() == "explorer")
                        {
                            Shell32.FolderItems items = ((Shell32.IShellFolderViewDual2)window.Document).SelectedItems();
                            foreach (Shell32.FolderItem item in items)
                            {

                                if (item.Path.StartsWith(System.Environment.CurrentDirectory))
                                {
                                    selected.Add(item.Path);
                                   // mylist.Add(item.Path);
                                   //  MessageBox.Show("FilePath: " + selected[selected.Count - 1]);
                                }

                                /*
                                MessageBox.Show(Environment.GetCommandLineArgs().GetValue(1).ToString());
                                int myint = Environment.GetCommandLineArgs().GetValue(1).ToString().LastIndexOf(".");
                                MessageBox.Show(myint.ToString());
                                string str = Environment.GetCommandLineArgs().GetValue(1).ToString().Remove(myint);
                                MessageBox.Show(str);
                                if (item.Path.StartsWith(str)) 
                                {
                                    MessageBox.Show(item.Path);
                                    selected.Add(item.Path);
                                }
                                 */

                                //  selected.Add(item.Path);
                            }
                        }
                    }
                    mylist.AddRange(selected);
                   // Thread.Sleep(TimeSpan.FromMilliseconds(3000));
                    //TotalLines("");
                    // if (!File.Exists("1.txt"))
                    // {
              ////      File.WriteAllLines("1.txt", mylist.ToArray());
                  //  test();

            ////        File.WriteAllText("2.txt", File.ReadAllText("1.txt"));
            ////        File.Delete("1.txt");
                    MessageBox.Show(mylist.Count.ToString()+": "+mylist[mylist.Count - 1]);

               //     Thread.Sleep(TimeSpan.FromMilliseconds(3000));
                 //   File.WriteAllText("3.txt", "Done!");
                   // Thread.Sleep(500);
                    File.Delete("1.txt");
                }
                catch (Exception exc)
                { 
                    MessageBox.Show(exc.Message);
                }
            }
        }
    }

Update=> This is what I want to do: Player Verb

Windows SDK Download Page

I will update this post when I completely handled my problem!

but at least & finally I got the solution I was looking for. Hope this thread help others too :)

My current Problem is that sample is written in C++, and I can't understand it well till now!

and I need to mix it with my application(written in C#). If it's possible!!??

Answer 1

Single app example

bool createdNew;

Mutex m = new Mutex(true, "YOURAPPNAME", out createdNew);

if (!createdNew)
{
    MessageBox.Show("already running!");
    return;
}