Convert.ToDouble geht in einenm Projekt im anderen nicht, warum?

Hi Robin,
try following console demo:

using System;
using System.Globalization;
using System.Windows.Forms;

namespace ConsoleApp1
{
  class Program28
  {
    static void Main(string[] args)
    {
      try
      {
        (new Demo()).Execute();
      }
      catch (Exception ex) { Console.WriteLine(ex.ToString()); }
      Console.WriteLine("Continue enter key");
      Console.ReadKey();
    }

    internal class Demo
    {
      internal void Execute()
      {
        string Tage_string = "1,234,567.89";

        // english OS
        Application.CurrentCulture = CultureInfo.InvariantCulture;
        try
        {
          double Tage_double = Convert.ToDouble(Tage_string);
          Console.WriteLine(Tage_double);
        }
        catch (Exception ex) { Console.WriteLine(ex.Message); }

        // german OS
        Application.CurrentCulture = CultureInfo.GetCultureInfo("de-de");
        try
        {
          double Tage_double = Convert.ToDouble(Tage_string);
          Console.WriteLine(Tage_double);
        }
        catch (Exception ex) { Console.WriteLine(ex.Message); }

        // german OS with IFormatProvider
        Application.CurrentCulture = CultureInfo.GetCultureInfo("de-de");
        try
        {
          double Tage_double = Convert.ToDouble(Tage_string, CultureInfo.InvariantCulture);
          Console.WriteLine(Tage_double);
        }
        catch (Exception ex) { Console.WriteLine(ex.Message); }

      }
    }
  }
}