iot/projects/Infrastructure/Extensions/Base64Extensions.cs

using System;
using System.Text;

namespace Infrastructure.Extensions
{
    public static class Base64Extensions
    {
        public static string Base64UrlEncode(this string input)
        {
            if (input is null)
            {
                throw new ArgumentNullException(nameof(input));
            }

            var output = Convert.ToBase64String(Encoding.UTF8.GetBytes(input));
            output = output.Split('=')[0];
            output = output.Replace('+', '-');
            output = output.Replace('/', '_');
            return output;
        }

        public static string Base64UrlDecode(this string input)
        {
            if (input is null)
            {
                throw new ArgumentNullException(nameof(input));
            }

            var output = input;
            output = output.Replace('-', '+');
            output = output.Replace('_', '/');
            switch (output.Length % 4)
            {
                case 0: break;
                case 2: output += "=="; break;
                case 3: output += "="; break;
                default: break;
            }
            var converted = Convert.FromBase64String(output);
            return Encoding.UTF8.GetString(converted);
        }
    }
}