WebAPI Gzip when returning HttpResponseMessage

Question

I have a WebAPI controller that returns an HttpResponseMessage and I want to add gzip compression. This is the server code:

using System.Net.Http;
u         


        

Answer 1

One Solution without editing any IIS Setting or Installing any Nuget package is to add a MessageHandler to your WEB API.

This will catch requests with the "AcceptEncoding" Header and compress them using the Build in System.IO.Compression libraries.

public class CompressHandler : DelegatingHandler
{
    private static CompressHandler _handler;
    private CompressHandler(){}
    public static CompressHandler GetSingleton()
    {
        if (_handler == null)
            _handler = new CompressHandler();
        return _handler;
    }
    protected override Task SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        return base.SendAsync(request, cancellationToken).ContinueWith((responseToCompleteTask) =>
        {
            HttpResponseMessage response = responseToCompleteTask.Result;
            var acceptedEncoding =GetAcceptedEncoding(response);
            if(acceptedEncoding!=null)
                response.Content = new CompressedContent(response.Content, acceptedEncoding);

            return response;
        },
        TaskContinuationOptions.OnlyOnRanToCompletion);
    }
    private string GetAcceptedEncoding(HttpResponseMessage response)
    {
        string encodingType=null;
        if (response.RequestMessage.Headers.AcceptEncoding != null && response.RequestMessage.Headers.AcceptEncoding.Any())
        {
            encodingType = response.RequestMessage.Headers.AcceptEncoding.First().Value;
        }
        return encodingType;
    }


}

    public class CompressedContent : HttpContent
{
    private HttpContent originalContent;
    private string encodingType;

    public CompressedContent(HttpContent content, string encodingType)
    {
        if (content == null)
        {
            throw new ArgumentNullException("content");
        }

        if (encodingType == null)
        {
            throw new ArgumentNullException("encodingType");
        }

        originalContent = content;
        this.encodingType = encodingType.ToLowerInvariant();

        if (this.encodingType != "gzip" && this.encodingType != "deflate")
        {
            throw new InvalidOperationException(string.Format("Encoding '{0}' is not supported. Only supports gzip or deflate encoding.", this.encodingType));
        }

        // copy the headers from the original content
        foreach (KeyValuePair> header in originalContent.Headers)
        {
            this.Headers.TryAddWithoutValidation(header.Key, header.Value);
        }

        this.Headers.ContentEncoding.Add(encodingType);
    }

    protected override bool TryComputeLength(out long length)
    {
        length = -1;

        return false;
    }

    protected override Task SerializeToStreamAsync(Stream stream, TransportContext context)
    {
        Stream compressedStream = null;

        if (encodingType == "gzip")
        {
            compressedStream = new GZipStream(stream, CompressionMode.Compress, leaveOpen: true);
        }
        else if (encodingType == "deflate")
        {
            compressedStream = new DeflateStream(stream, CompressionMode.Compress, leaveOpen: true);
        }

        return originalContent.CopyToAsync(compressedStream).ContinueWith(tsk =>
        {
            if (compressedStream != null)
            {
                compressedStream.Dispose();
            }
        });
    }
}

And add this handler to your Global.asax.cs

GlobalConfiguration.Configuration.MessageHandlers.Insert(0, CompressHandler.GetSingleton());

Kudos to Ben Foster. ASP.NET Web API Compression