gistfile1.cs

namespace Syndication.Client.Http
{
    public class CachingAdapter : HttpClientAdapter
    {
        readonly HttpClient client;   

        public CachingAdapter(ICacheStore cacheStore,  string[] defaultVaryHeaders) 
        {
            //http://msdn.microsoft.com/en-us/library/system.net.cache.requestcachelevel(v=vs.110).aspx
            //http://blog.technovert.com/2013/01/httpclient-caching/
            //http://blogs.msdn.com/b/henrikn/archive/2012/08/07/httpclient-httpclienthandler-and-httpwebrequesthandler.aspx

            if(cacheStore == null)
             client = new HttpClient();
            else
            {
                client = new HttpClient(new CustomCachingHandler(cacheStore)
                {
                    DefaultVaryHeaders = defaultVaryHeaders,

                    InnerHandler = new HttpClientHandler()
                });  
            }
        }

        public void Dispose()
        {
            client.Dispose();
        }

        public Task<HttpResponseMessage> SendAsync(HttpRequestMessage request)
        {
            return client.SendAsync(request).ContinueWith(task => new ResponseDecompressor().DecompressResponse(task));
        }

    }
}

namespace Syndication.Client.Http
{
    public class Factory : HttpClientAdapterFactory
    {
        readonly ICacheStore _cacheStore;
        private readonly string[] _defaultVaryHeaders;

        public Factory(ICacheStore cacheStore, string[] defaultVaryHeaders)
        {
            _cacheStore = cacheStore;
            _defaultVaryHeaders = defaultVaryHeaders;
        }

        public HttpClientAdapter CreateClient(PipelineOptions options)
        {
            return new CachingAdapter(_cacheStore, _defaultVaryHeaders);
        }
    }
}