using System;

using System.Text;

using Microsoft.AspNetCore.WebUtilities;

public class Program

{

    public static void Main()

    {

        var s = "W0JFTEVHX05SX109IkU4NDE3NyI";

        var o = @"[BELEG_NR_]=""E84177""";

        Console.WriteLine("Decoding Start ==============================================");Console.WriteLine("\r\n");

        Console.WriteLine(".NET 4.8 - FromBase64String:");

        Console.WriteLine($@"""{s}="" => {Encoding.UTF8.GetString(Convert.FromBase64String($"{s}="))}");

        try { Console.WriteLine($@"""{s}"" => {Encoding.UTF8.GetString(Convert.FromBase64String(s))}"); }

        catch (Exception ex) { Console.WriteLine($@"""{s}"" => Error: {ex.Message}"); }

        try { Console.WriteLine($@"""{s}%3d"" => {Encoding.UTF8.GetString(Convert.FromBase64String($"{s}%3d"))}"); }

        catch (Exception ex) { Console.WriteLine($@"""{s}%3d"" => Error: {ex.Message}"); }

        Console.WriteLine("\r\n");

        Console.WriteLine(".NET CORE - Base64UrlDecode:");

        Console.WriteLine($@"""{s}="" => {Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode($"{s}="))}");

        Console.WriteLine($@"""{s}"" => {Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(s))}");

        try { Console.WriteLine($@"""{s}%3d"" => {Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode($"{s}%3d"))}"); }

        catch (Exception ex) { Console.WriteLine($@"""{s}%3d"" => Error: {ex.Message}"); }

        Console.WriteLine("\r\n");

        Console.WriteLine("Decoding End ================================================");

        Console.WriteLine("\r\n");

        Console.WriteLine("Encoding Start ==============================================");

        Console.WriteLine("\r\n");

        Console.WriteLine(".NET 4.8 - ToBase64String:");        

        Console.WriteLine($@"{o} => {Convert.ToBase64String(Encoding.UTF8.GetBytes(o))}");

        Console.WriteLine("\r\n");

        Console.WriteLine(".NET CORE - Base64UrlEncode:");

        Console.WriteLine($@"{o} => {WebEncoders.Base64UrlEncode(Encoding.UTF8.GetBytes(o))}");

        Console.WriteLine("\r\n");

        Console.WriteLine("Encoding End ================================================");

    }

}