using static System.Console;

using System;

using System.Text;

​

public static class Base64ExtensionMethods

{

    public static string ConvertToBase64String(this string toBase64Str) => Convert.ToBase64String(Encoding.ASCII.GetBytes(toBase64Str)); //converting binary data as base64

    public static string ConvertFromBase64String(this string fromBase64Str) =>  ASCIIEncoding.ASCII.GetString(Convert.FromBase64String(fromBase64Str));

}

​

public class Program

{

    public static void Main()

    {

        var stringConvertedToBase64 = "Hello World!".ConvertToBase64String();

        WriteLine("String converted to Base64 String: " + stringConvertedToBase64);

        WriteLine("Decoded message from Base64 String: " + stringConvertedToBase64.ConvertFromBase64String());          

    }

}