private ContentInfo GetContentInfoFromRequest(HttpRequestMessage request, long entityLength)
        {
            var result = new ContentInfo
                        {
                            From = 0, To = entityLength - 1,
                            IsPartial = false, Length = entityLength
                        };
            RangeHeaderValue rangeHeader = request.Headers.Range;
            if (rangeHeader != null && rangeHeader.Ranges.Count != 0)
            {
                //we support only one range
                if (rangeHeader.Ranges.Count > 1)
                {
                    //we probably return other status code here
                    throw new HttpResponseException(HttpStatusCode.RequestedRangeNotSatisfiable);
                }
                RangeItemHeaderValue range = rangeHeader.Ranges.First();
                if (range.From.HasValue && range.From < 0 || range.To.HasValue && range.To > entityLength - 1)
                {
                    throw new HttpResponseException(HttpStatusCode.RequestedRangeNotSatisfiable);
                }

                result.From = range.From ?? 0;
                result.To = range.To ?? entityLength - 1;
                result.IsPartial = true;
                result.Length = entityLength;
                if (range.From.HasValue && range.To.HasValue)
                {
                    result.Length = range.To.Value - range.From.Value + 1;
                }
                else if (range.From.HasValue)
                {
                    result.Length = entityLength - range.From.Value + 1;
                }
                else if (range.To.HasValue)
                {
                    result.Length = range.To.Value + 1;
                }
            }

            return result;
        }
        private void SetResponseHeaders(HttpResponseMessage response, ContentInfo contentInfo,
            long fileLength, string fileName,byte[] hash)
        {
            response.Headers.AcceptRanges.Add("bytes");
            response.StatusCode = contentInfo.IsPartial ? HttpStatusCode.PartialContent
                : HttpStatusCode.OK;
            response.Content.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment");
            response.Content.Headers.ContentDisposition.FileName = fileName;
            response.Content.Headers.ContentType = new MediaTypeHeaderValue("application/octet-stream");
            response.Content.Headers.ContentLength = contentInfo.Length;

            if (hash.Length > 0)
                response.Content.Headers.ContentMD5 = hash;

            if (contentInfo.IsPartial)
            {
                response.Content.Headers.ContentRange
                    = new ContentRangeHeaderValue(contentInfo.From, contentInfo.To, fileLength);
            }
        }