using System;

​

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Decoded string: " + Base64Decode("MTEzNTAy"));

    }

     public static string Base64Decode(string base64EncodedData)

        {

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

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

        }

}