Rate Limiter written in c#

RateLimiter.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Threading;

namespace YourNamespaceHere
{
    [Serializable()]
    public class RateLimiter
    {
        public RateLimiter(Int32 requests, TimeSpan interval)
        {
            this.Requests = requests;
            this.Interval = interval;
        }

        public Int32 Requests { get; set; }
        public TimeSpan Interval { get; set; }

        private ReaderWriterLockSlim _lock = new ReaderWriterLockSlim(LockRecursionPolicy.SupportsRecursion);
        private Dictionary<String, Queue<DateTime>> _internalStorage = new Dictionary<String, Queue<DateTime>>();

        public Boolean Process(String address)
        {
            _lock.EnterUpgradeableReadLock();
            try
            {
                if (!_internalStorage.ContainsKey(address))
                {
                    _lock.EnterWriteLock();
                    try
                    {
                        _internalStorage.Add(address, new Queue<DateTime>());
                        _internalStorage[address].Enqueue(DateTime.Now);
                        return true;
                    }
                    finally
                    {
                        _lock.ExitWriteLock();
                    }
                }
                else
                {
                    PurgeOldEntries(address);

                    _lock.EnterWriteLock();
                    try
                    {
                        _internalStorage[address].Enqueue(DateTime.Now);
                        return _internalStorage[address].Count <= Requests;
                    }
                    finally
                    {
                        _lock.ExitWriteLock();
                    }
                }
            }
            finally
            {
                _lock.ExitUpgradeableReadLock();
            }
        }

        private void PurgeOldEntries(String address)
        {
            _lock.EnterWriteLock();
            try
            {
                while (_internalStorage[address].Count > 0 && (DateTime.Now - _internalStorage[address].Peek() > Interval))
                {
                    _internalStorage[address].Dequeue();
                }
            }
            finally
            {
                _lock.ExitWriteLock();
            }
        }
    }
}

Is there an example on how to use this? The following doesn't seem to work and the queue appears to just continue piling up.

static void Main()
{
    var limiter = new RateLimiter(10, TimeSpan.FromSeconds(5));

    var t = Task.Run(() =>
    {
        for (var i = 0; i < 100; i++)
        {
            while (!limiter.Process("foo"))
            {
                Task.Delay(1).Wait();
            }

            Console.WriteLine(i);
        }
    });

    Task.WaitAll(t);
    Console.ReadKey();
}