Posting compressed data in JSON format to the ASP.NET website using WinForm

We have posted an article on how to post JSON data from WinForm to ASP.NET/ASHX in 2015 (as shown below). In the earlier article, it does not optimize the payload size and reduce the communication time.

    http://laucsharp.blogspot.my/2015/07/posting-data-in-json-format-to-aspnet.html

In order to speed up the communication between the WinForm client and ASP.NET/ASHX, we must reduce the payload size.To do that, the contents must be compressed before we upload the data and decompress upon receiving it.

There are 2 compression algorithms for HTTP/HTTPS communication: gzip and deflat.

Here is the code to compress the contents with GZip algorithm. You need this code in both WinForm and ASP.NET/ASHX.

        public static void GZip(Stream stream, string data)
        {
            byte[] b = System.Text.Encoding.UTF8.GetBytes(data);
            GZip(stream, b);
        }

        public static void GZip(Stream stream, byte[] data)
        {
            using (var zipStream = new GZipStream(stream, CompressionMode.Compress, true))
            {
                zipStream.Write(data, 0, data.Length);
            }
        }
To decompress the GZip contents. You need this code in both WinForm and ASP.NET/ASHX.

        public static string GUnZipToString(Stream stream)
        {
            byte[] b = GUnZip(stream);
            return System.Text.Encoding.UTF8.GetString(b);
        }

        public static byte[] GUnZip(Stream stream)
        {
            using (var zipStream = new GZipStream(stream, CompressionMode.Decompress, true))
            using (MemoryStream ms = new MemoryStream())
            {
                zipStream.CopyTo(ms);
                return ms.ToArray();
            }
        }
In the WinForm app, we used to write the JSON data directly to the HttpWebRequest like this:

        // write the json data into the request stream.
        using (StreamWriter writer = new StreamWriter(request.GetRequestStream()))
        {
                writer.Write(json_data);
        }

In order to reduce the payload, we should write the compressed data by doing this:

        // to indicate we accept gzip content.
        request.Headers.Add(HttpRequestHeader.AcceptEncoding, "gzip");

        // to indicate that the content is compressed using gzip algorithm.
        request.Headers.Add("Content-Encoding", "gzip");

        GZip(request.GetRequestStream(), json_data);

 In the ASP.NET/ASHX, we used to read the contents like this:

        // get the contents from the request stream
        Stream stream = context.Request.InputStream;
        using (StreamReader r = new StreamReader(stream))
        {
            s = r.ReadToEnd();
        }

Now, we have to read the contents and then decompress it. "Content-Encoding" is the indicator whether the contents is in GZip, deflat or not compress.

        if (HelperFunc.IsGZipContent(context))
        {
                 // read the compressed content.
                s = GUnZipToString(context.Request.InputStream);          
        }
         else
        {
                // get the contents from the request stream
                Stream stream = context.Request.InputStream;
                using (StreamReader r = new StreamReader(stream))
                {
                        s = r.ReadToEnd();
                }
        }

Here is the function to check whether the contents is compressed in GZip format. Please take note that the sample codes in this article did not support "deflat" algorithm.

        public static bool IsGZipContent(System.Web.HttpContext ctx)
        {
            string enc = ctx.Request.Headers["Content-Encoding"];

            if (string.IsNullOrEmpty(enc))
            {
                return false;
            }

            return  enc.ToLower().Contains("gzip");
        }

You will find more information about the static and dynamic compression in IIS:

   https://docs.microsoft.com/en-us/iis/configuration/system.webserver/httpcompression/

To find out why we need to compress the data, please refers to the following link:

   https://developer.mozilla.org/en-US/docs/Web/HTTP/Compression