using System;

using System.IO;

using System.IO.Compression;

using System.Text;

public class Program

{

    public static void Main()

    {

        Console.WriteLine(Compress("ciao mamma"));

        Console.WriteLine(Decompress("H4sIAAAAAAAEAEvOTMxXyE3MzU0EAChGWAcKAAAA"));

    }

​

    public static string Compress(string s)

    {

        var bytes = Encoding.UTF8.GetBytes(s);

        using (var msi = new MemoryStream(bytes))

        using (var mso = new MemoryStream())

        {

            using (var gs = new GZipStream(mso, CompressionMode.Compress))

            {

                msi.CopyTo(gs);

            }

            return Convert.ToBase64String(mso.ToArray());

        }

    }

​

    public static string Decompress(string s)

    {

        var bytes = Convert.FromBase64String(s);

        using (var msi = new MemoryStream(bytes))

        using (var mso = new MemoryStream())

        {

            using (var gs = new GZipStream(msi, CompressionMode.Decompress))

            {

                gs.CopyTo(mso);

            }

            return Encoding.UTF8.GetString(mso.ToArray());

        }

    }

}

​