patch to https://bitbucket.org/pwalat/piotr.webapihmacauth

ResponseContentMd5Handler.cs

    public class ResponseContentMd5Handler : DelegatingHandler
    {
        protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request,
            System.Threading.CancellationToken cancellationToken)
        {
            HttpResponseMessage response = await base.SendAsync(request, cancellationToken);

            if (response.IsSuccessStatusCode && response.Content != null)
            {
                response.Content.Headers.ContentMD5 = await MD5Helper.ComputeHash(response.Content);
            }
            return response;
        }
    }