Custom Synchronized Cache

SynchronizedCache.cs

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using System.Threading;

namespace TestCustomCache
{
    public sealed class CacheSingleton
    {
        private static readonly SynchronizedCache instance = new SynchronizedCache();

        static CacheSingleton()
        {
        }

        private CacheSingleton()
        {
        }

        public static SynchronizedCache Instance
        {
            get
            {
                return instance;
            }
        }
    }


    public class SynchronizedCache
    {
        private ReaderWriterLockSlim cacheLock = new ReaderWriterLockSlim();
        private Dictionary<string, string> innerCache = new Dictionary<string, string>();

        public int Count
        { get { return innerCache.Count; } }

        public string Read(string key)
        {
            cacheLock.EnterReadLock();
            try
            {

                string result = null;
                innerCache.TryGetValue(key, out result);
                return result;
            }
            finally
            {
                cacheLock.ExitReadLock();
            }
        }

        public void Add(string key, string value)
        {
            cacheLock.EnterWriteLock();
            try
            {
                innerCache.Add(key, value);
            }
            finally
            {
                cacheLock.ExitWriteLock();
            }
        }


        ~SynchronizedCache()
        {
            if (cacheLock != null) cacheLock.Dispose();
        }
    }
}