using System;

using System.Collections.Generic;

using System.IO;

using System.IO.Compression;

using System.Text;

public class Program

{

    public static void Main()

    {

        var bytes = Encoding.UTF8.GetBytes("<bazinga>This is a test</bazinga>");

        using (var output = new MemoryStream())

        {

            using (var zip = new DeflateStream(output, CompressionMode.Compress))

            {

                zip.Write(bytes, 0, bytes.Length);

            }

            var base64 = Convert.ToBase64String(output.ToArray());

​

            Console.WriteLine(base64);

        }

    }

}