问Web API的压缩筛选器

EN

public class CompressAPIAttribute : System.Web.Http.Filters.ActionFilterAttribute
{
    public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext filterContext)
    {
        var preferredEncoding = GetPreferredEncoding(filterContext.Request);
        Stream compressedStream = null;
        // Compress the response accordingly
        var response = filterContext.Response;
        response.Headers.Add("Content-encoding", preferredEncoding.ToString());

        if (preferredEncoding == CompressionScheme.Gzip)
        {
            response.Content = new GZipStream(compressedStream, CompressionMode.Compress); //THIS WON'T WORK
        } 

        if (preferredEncoding == CompressionScheme.Deflate)
        {
            response.Content = new DeflateStream(compressedStream, CompressionMode.Compress); //THIS WON'T WORK
        }
        return;
    }

    enum CompressionScheme
    {
        Gzip = 0,
        Deflate = 1,
        Identity = 2
    }

    private CompressionScheme GetPreferredEncoding(HttpRequestMessage request)
    {
        var acceptableEncoding = request.Headers.AcceptEncoding;

        if (acceptableEncoding.Where(h => h.Value.Contains("gzip")).Count() > 0)
            return CompressionScheme.Gzip;

        if (acceptableEncoding.Where(h => h.Value.Contains("deflate")).Count() > 0)
            return CompressionScheme.Deflate;

        return CompressionScheme.Identity;
    }