using static System.Console;
public static class Base64ExtensionMethods
public static string ConvertToBase64String(this string toBase64Str) => Convert.ToBase64String(Encoding.ASCII.GetBytes(toBase64Str));
public static string ConvertFromBase64String(this string fromBase64Str) => ASCIIEncoding.ASCII.GetString(Convert.FromBase64String(fromBase64Str));
public static void Main()
var stringConvertedToBase64 = "Hello World!".ConvertToBase64String();
WriteLine("String converted to Base64 String: " + stringConvertedToBase64);
WriteLine("Decoded message from Base64 String: " + stringConvertedToBase64.ConvertFromBase64String());