LazyCache

gistfile1.cs

using System;
using System.Runtime.Caching;

namespace Euromoney.Isis.Api.Services
{
    public abstract class LazyCache
    {
        protected static readonly object ValueLock = new object();
    }

    public sealed class LazyCache<T> : LazyCache
    {
        private readonly string _key;
        private readonly Func<T> _valueFactory;
        private readonly TimeSpan _cacheLength;
      
        private readonly ObjectCache _cache = MemoryCache.Default;

        public LazyCache(string key, Func<T> valueFactory, TimeSpan cacheLength)
        {
            _key = "LazyCache"+key;
            _valueFactory = valueFactory;
            _cacheLength = cacheLength;
        }

        public T Value
        {
            get
            {
                if (IsCached())
                {
                    return (T)_cache[_key];
                }

                lock (ValueLock)
                {
                    if (!IsCached())
                    {
                        var value = _valueFactory.Invoke();
                        _cache.Add(_key, value, DateTimeOffset.UtcNow.Add(_cacheLength));
                    }
                }

                return (T)_cache[_key];
            }
        }

        private bool IsCached()
        {
            return _cache.Contains(_key);
        }
    }
}