WCF thread safety in 25 lines of code

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall, ConcurrencyMode = ConcurrencyMode.Single)]
public class ThreadSafeService : IServiceContract
{
    private int counter;

    [MethodImpl(MethodImplOptions.Synchronized)]
    public void IncrementCounter(int amount)
    {
        Mutex m = new Mutex(false);
        try
        {
            Monitor.Enter(this);
            m.WaitOne();
            lock (this)
            {
                Interlocked.Add(ref counter, amount);
            }
        }
        finally
        {
            m.ReleaseMutex();
            Monitor.Exit(this);
        }
    }
}

I dare to say that familiarity with every technique used in this sample would make you comfortable in dealing with WCF multithreading and throughput issues.