System.Net.Http.HttpHandlerToFilter.CreateRequestContentAsync C# (CSharp) Method

        private static async Task<RTIHttpContent> CreateRequestContentAsync(HttpRequestMessage request, HttpRequestHeaderCollection rtHeaderCollection)
        {
            HttpContent content = request.Content;

            RTIHttpContent rtContent;
            ArraySegment<byte> buffer;

            // If we are buffered already, it is more efficient to send the data directly using the buffer with the
            // WinRT HttpBufferContent class than using HttpStreamContent. This also avoids issues caused by
            // a design limitation in the System.Runtime.WindowsRuntime System.IO.NetFxToWinRtStreamAdapter.
            if (content.TryGetBuffer(out buffer))
            {
                rtContent = new RTHttpBufferContent(buffer.Array.AsBuffer(), (uint)buffer.Offset, (uint)buffer.Count);
            }
            else
            {
                Stream contentStream = await content.ReadAsStreamAsync().ConfigureAwait(false);
                
                if (contentStream is RTIInputStream)
                {
                    rtContent = new RTHttpStreamContent((RTIInputStream)contentStream);
                }
                else if (contentStream is MemoryStream)
                {
                    var memStream = contentStream as MemoryStream;
                    if (memStream.TryGetBuffer(out buffer))
                    {
                        rtContent = new RTHttpBufferContent(buffer.Array.AsBuffer(), (uint)buffer.Offset, (uint)buffer.Count);
                    }
                    else
                    {
                        byte[] byteArray = memStream.ToArray();
                        rtContent = new RTHttpBufferContent(byteArray.AsBuffer(), 0, (uint) byteArray.Length);
                    }
                }
                else
                {
                    rtContent = new RTHttpStreamContent(contentStream.AsInputStream());
                }
            }

            // RTHttpBufferContent constructor automatically adds a Content-Length header. RTHttpStreamContent does not.
            // Clear any 'Content-Length' header added by the RTHttp*Content objects. We need to clear that now
            // and decide later whether we need 'Content-Length' or 'Transfer-Encoding: chunked' headers based on the
            // .NET HttpRequestMessage and Content header collections.
            rtContent.Headers.ContentLength = null;

            // Deal with conflict between 'Content-Length' vs. 'Transfer-Encoding: chunked' semantics.
            // Desktop System.Net allows both headers to be specified but ends up stripping out
            // 'Content-Length' and using chunked semantics.  The WinRT APIs throw an exception so
            // we need to manually strip out the conflicting header to maintain app compatibility.
            if (request.Headers.TransferEncodingChunked.HasValue && request.Headers.TransferEncodingChunked.Value)
            {
                content.Headers.ContentLength = null;
            }
            else
            {
                // Trigger delayed header generation via TryComputeLength. This code is needed due to an outstanding
                // bug in HttpContentHeaders.ContentLength. See GitHub Issue #5523.
                content.Headers.ContentLength = content.Headers.ContentLength;
            }

            foreach (KeyValuePair<string, IEnumerable<string>> headerPair in content.Headers)
            {
                foreach (string value in headerPair.Value)
                {
                    if (!rtContent.Headers.TryAppendWithoutValidation(headerPair.Key, value))
                    {
                        // rtContent headers are restricted to a white-list of allowed headers, while System.Net.HttpClient's content headers 
                        // will allow custom headers.  If something is not successfully added to the content headers, try adding them to the standard headers.
                        bool success = rtHeaderCollection.TryAppendWithoutValidation(headerPair.Key, value);
                        Debug.Assert(success);
                    }
                }
            }
            return rtContent;
        }