Program.cs

[MethodImpl(MethodImplOptions.AggressiveOptimization)]
static void SyncMethod()
{
    // Run a garbage collection in 1 second
    Task.Delay(1000).ContinueWith(_ => { GC.Collect(); });

    var taskCompletionSource = new TaskCompletionSource();

    Action myDelegate = () => taskCompletionSource.SetResult();

    MyNativeMethod(new WeakReference(myDelegate));

    taskCompletionSource.Task.Wait(); // Wait synchronously on the TCS

    GC.KeepAlive(myDelegate);
}