Generic interface for identifying messages that participate in caching operations.

CachableRequestHandler.cs

    public class CachableRequestHandler<TRequest, TResponse>
        : IAsyncRequestHandler<TRequest, TResponse>
            where TRequest : IAsyncRequest<TResponse>, ICacheable<TRequest>
            where TResponse : class
    {
        private readonly IAsyncRequestHandler<TRequest, TResponse> innerHandler;
        private readonly ObjectCache objectCache;

        private readonly ReaderWriterLockSlim cacheLock = new ReaderWriterLockSlim();

        public CachableRequestHandler(IAsyncRequestHandler<TRequest, TResponse> innerHandler, ObjectCache objectCache)
        {
            this.innerHandler = innerHandler;
            this.objectCache = objectCache;
        }

        Task<TResponse> IAsyncRequestHandler<TRequest, TResponse>.Handle(TRequest message)
        {
            var cacheKey = message.GetCacheKey();

            cacheLock.EnterReadLock();
            TResponse cachedResult = this.objectCache.Get(cacheKey, null) as TResponse;
            cacheLock.ExitReadLock();

            if (cachedResult == null)
            {
                cacheLock.EnterWriteLock();
                try
                {
                    cachedResult = this.innerHandler.Handle(message).Result;

                    var policy = message.GetPolicy();

                    this.objectCache.Set(cacheKey, cachedResult, policy);
                }
                finally
                {
                    cacheLock.ExitWriteLock();
                }
            }

            return Task.FromResult(cachedResult);
        }
    }

ICacheable.cs

    public interface ICacheable<T>
    {
        CacheItemPolicy GetPolicy();
        string GetCacheKey();
    }