Coding Challange 6 - C#

/*
 * The Morpheus Tutorials:  https://www.youtube.com/channel/UCLGY6_j7kZfA1dmmjR1J_7w
 * Coding Challange 6:      https://www.youtube.com/watch?v=sdAXkE39b9k
 * Version:                 2018.08.11.1954
 */

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Net.Http;
using System.Text;

using static System.Console;
using static System.Math;

namespace Challange_6 {

  internal class Program {
    private const string CHALLANGES = "https://cc.the-morpheus.de/challenges/6/";
    private const string SOLUTIONS = "https://cc.the-morpheus.de/solutions/6/";

    private static readonly HttpClient client = new HttpClient();
    private static readonly Stopwatch watch = new Stopwatch();

    private static void Main(string[] args) {
      try {
        do {
          string numStr = client.GetStringAsync(CHALLANGES).Result;

          watch.Restart();                                                  // Start Konvertierung
          ulong number = MyConverter.Str2Dec(numStr);
          watch.Stop();
          double timeToNumber = watch.Elapsed.TotalMilliseconds;

          watch.Restart();
          string binary = MyConverter.Dec2Bin(number);
          watch.Stop();                                                     // Ende Konvertierung
          double timeToBinary = watch.Elapsed.TotalMilliseconds;

          string response = client.PostAsync(SOLUTIONS, new StringContent(
            $@"{{ ""token"": ""{binary}"" }}",
            Encoding.UTF8,
            "application/json")).Result.Content.ReadAsStringAsync().Result;

          string message = $"Number: {number} ({timeToNumber}ms)\nBinary: {binary} ({timeToBinary}ms)\nResult: {response}\n";
          WriteLine(message);
        } while (ReadKey().Key != ConsoleKey.Escape);
      } catch (Exception ex) {
        WriteLine(ex);
        ReadKey();
      }
    }
  }

  internal static class MyConverter {

    public static ulong Str2Dec(string numStr) {
      ulong number = 0;
      ulong power = 1;
      for (int i = numStr.Length - 1; i >= 0; i--) {
        int num = numStr[i] - '0';
        if (num >= 0 && num <= 9) {
          number += (ulong)num * power;
          power *= 10;
        }
      }

      return number;
    }

    public static string Dec2Bin(ulong number) {
      int count = (int)Ceiling(Log10(number) / Log10(2));                   // Anzahl der Bits bestimmen
      char[] numbers = new char[count];

      ulong temp = number;
      for (int i = count - 1; i >= 0; i--) {
        numbers[i] = (char)('0' + (temp & 1));                              // Bit für Position bestimmen
        temp >>= 1;                                                         // Bitshift um eine Position (entspricht Division durch 2)
      }

      return new string(numbers);
    }
  }
}