OnStartStop.cs

protected override void OnStart()
{
    string sessionName = $"GcLogEtwSession_{_pid.ToString()}_{Guid.NewGuid().ToString()}";
    Console.WriteLine($"Starting {sessionName}...\r\n");
    _userSession = new TraceEventSession(sessionName, TraceEventSessionOptions.Create);

    Task.Run(() =>
    {
        // only want to receive GC event
        ClrEventsManager manager = new ClrEventsManager(_userSession, _pid, EventFilter.GC);
        manager.GarbageCollection += OnGarbageCollection;

        // this is a blocking call until the session is disposed
        manager.ProcessEvents();
        Console.WriteLine("End of CLR event processing");
    });

    // add a header to the .csv file
    WriteLine(Header);
}

protected override void OnStop()
{
    // when the session is disposed, the call to ProcessEvents() returns
    _userSession.Dispose();
}