URL Friendly Base64'ness

file.cs

    public static class Base64Extension
    {
        static readonly char[] padding = { '=' };
        public static string EncodeURLBase64(this string Input)
        {
            var base64 = Convert.ToBase64String(Encoding.Default.GetBytes(Input)).TrimEnd(padding).Replace('+', '-').Replace('/', '_');
            return base64;
        }

        public static string DecodeURLBase64(this string Input)
        {
            string incoming = Input.Replace('_', '/').Replace('-', '+');
            switch (Input.Length % 4)
            {
                case 2: incoming += "=="; break;
                case 3: incoming += "="; break;
            }
            byte[] bytes = Convert.FromBase64String(incoming);
            string originalText = Encoding.Default.GetString(bytes);
            return originalText;
        }
    }