Communication between shell and app (winform)

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WinForms

C#7.0

I want to create a winform shell (shell) which could run other winform application (App1) inside it (on a panel) using Process.Start(startInfo);
Note: Using reference to App1.exe is not an option.

Shell want to listen to the events n messages of App1, what is the best way to accomplish it?

What are the down sides of using MemoryMappedFile?

Shell Code-
 using (MemoryMappedFile mmf = MemoryMappedFile.CreateOrOpen("AppWinShell", 1024))
            using (MemoryMappedViewStream view = mmf.CreateViewStream())
            {
                BinaryReader reader = new BinaryReader(view);
                EventWaitHandle signal = new EventWaitHandle(false, EventResetMode.AutoReset, "WinShellEvent");
                Mutex mutex = new Mutex(false, "WinShellMutex");

                while (true)
                {
                    signal.WaitOne();
                    mutex.WaitOne();
                    reader.BaseStream.Position = 0;
                    string message = reader.ReadString();
                    WriteTextSafe(message);
                    mutex.ReleaseMutex();
                }
            }
App1 code -

        private void SendMessage()
        {
            using (MemoryMappedFile mmf = MemoryMappedFile.CreateOrOpen("AppWinShell", 1024))
            using (MemoryMappedViewStream view = mmf.CreateViewStream())
            {
                BinaryWriter writer = new BinaryWriter(view);
                EventWaitHandle signal = new EventWaitHandle(false, EventResetMode.AutoReset, "WinShellEvent");
                Mutex mutex = new Mutex(false, "WinShellMutex");

                mutex.WaitOne();
                writer.BaseStream.Position = 0;
                System.Diagnostics.Process p = System.Diagnostics.Process.GetCurrentProcess();
                writer.Write(PID + "^" + txtMessage.Text);
                signal.Set();
                mutex.ReleaseMutex();

                Thread.Sleep(10);
            }
        }

Thoughts?

What I have tried:

Memory mapped file, EventWaitHandle, Mutex