using System;

using System.IO;

using System.IO.Compression;

using System.Text;

​

public class Program

{

    public static void Main()

    {

        string data = "Hello World!";

        Console.WriteLine(  Compression.CompressData(data, CompressionLevel.Fastest) );

        Console.WriteLine(  Compression.CompressData(data, CompressionLevel.NoCompression) );

        Console.WriteLine(  Compression.CompressData(data, CompressionLevel.Optimal) );

        // result would be DAAAAB+LCAAAAAAABADzSM3JyVcIzy/KSVEEAKMcKRwMAAAA

        // but I get       H4sIACwuuWAC//NIzcnJVwjPL8pJUQQAoxwpHAwAAAA=

    }

}

​

public class Compression

    {

        #region Member Variables

        /// <summary>The compressed message header length.</summary>

        private const int CompressedMessageHeaderLength = 0; // changed to zero

        #endregion

​

        #region Methods

        /// <summary>Compresses the XML string.</summary>

        /// <param name="documentToCompress">The XML string to compress.</param>

        public static string CompressData(string data, CompressionLevel compressionLevel)

        {

            using (MemoryStream memoryStream = new MemoryStream())

            {

                byte[] plainBytes = Encoding.UTF8.GetBytes(data);

​

                using (GZipStream zipStream = new GZipStream(memoryStream, compressionLevel, leaveOpen: true))

                {

                    zipStream.Write(plainBytes, 0, plainBytes.Length);

                }

​

                memoryStream.Position = 0;

​

                byte[] compressedBytes = new byte[memoryStream.Length + CompressedMessageHeaderLength];

​

                Buffer.BlockCopy(

                    BitConverter.GetBytes(plainBytes.Length),

                    0,

                    compressedBytes,

                    0,

                    CompressedMessageHeaderLength

                );

​

                // Add the header, which is the length of the compressed message.

                memoryStream.Read(compressedBytes, CompressedMessageHeaderLength, (int)memoryStream.Length);

​

                string compressedXml = Convert.ToBase64String(compressedBytes);

​

                return compressedXml;

            }

        }

        #endregion

    }