using System;

public class Program

{

    public static void Main()

    {

        //Console.WriteLine("Hello World");

        Console.WriteLine(Base64Encode("ABCDEF"));

        Console.WriteLine(Base64Decode("QUJDREVG"));

    }

    public static string Base64Encode(string plainText) {

      var plainTextBytes = System.Text.Encoding.UTF8.GetBytes(plainText);

      return System.Convert.ToBase64String(plainTextBytes);

    }

​

    public static string Base64Decode(string base64EncodedData) {

      var base64EncodedBytes = System.Convert.FromBase64String(base64EncodedData);

      return System.Text.Encoding.UTF8.GetString(base64EncodedBytes);

    }

​

}