How can I replace this semaphore with a monitor?

Question

In previous question of mine, someone had meantioned that using Semaphores were expensive in C# compared to using a monitor. So I ask this, how can I replace the semaphore in this code with a monitor?

I need function1 to return its value after function2 (in a separate thread) has been completed. I had replaced the Semaphore.WaitOne with a Monitor.Wait and the Semaphore.Release with a Monitor.PulseAll but the PulseAll was being triggered before the Wait causing the program to hang. Any idea how to avoid that race condition?

Semaphore semaphore = new Semaphore(0,1);
byte b;
public byte Function1()
{
    // new thread starting in Function2;

    semaphore.WaitOne();
    return b;
}

public void Function2()
{
    // do some thing
    b = 0;
    semaphore.Release();
}

Answer 1

You can do this with a WaitHandle instead of a Semaphore. This would be the simplest alternative, and perform better than a Semaphore:

ManualResetEvent manualResetEvent = new ManualResetEvent(false);
byte b;
public byte Function1()
{
    // new thread starting in Function2;

    manualResetEvent.WaitOne();
    return b;
}

public void Function2()
{
    // do some thing
    b = 0;
    manualResetEvent.Set();
}