public class DeflateCompressionAttribute : ActionFilterAttribute
    {

        public override void OnActionExecuted(HttpActionExecutedContext actContext)
        {
            var content = actContext.Response.Content;
            var bytes = content == null ? null : content.ReadAsByteArrayAsync().Result;
            var zlibbedContent = bytes == null ? new byte[0] :
            CompressionHelper.DeflateByte(bytes);
            actContext.Response.Content = new ByteArrayContent(zlibbedContent);
            actContext.Response.Content.Headers.Remove("Content-Type");
            actContext.Response.Content.Headers.Add("Content-encoding", "deflate");
            actContext.Response.Content.Headers.Add("Content-Type", "application/json");
            base.OnActionExecuted(actContext);
        }
    }

public class CompressionHelper
    {
        public static byte[] DeflateByte(byte[] str)
        {
            if (str == null)
            {
                return null;
            }
            using (var output = new MemoryStream())
            {
                using (
                    var compressor = new Ionic.Zlib.DeflateStream(
                    output, Ionic.Zlib.CompressionMode.Compress,
                    Ionic.Zlib.CompressionLevel.BestSpeed))
                {
                    compressor.Write(str, 0, str.Length);
                }

                return output.ToArray();
            }
        }
    }

   [DeflateCompression]
        public string Get(int id)
        {
            return "ok"+id;
        }