Change thread culture .NET Framework 4.6 and later versions

Question

I'm trying to change a new thread CultureInfo like the sample below but:

• Attempt1: SetCulture1() is not changing my thread

• Attempt2: SetCulture2() I got the exception "System.InvalidOperationException: instance is read-only" (when set CurrencyDecimalSeparator)

  static void Main(string[] args)
  {
      Thread th = new Thread(thread_test);
  
      // nothing happens
      SetCulture1(th);
  
      // exception System.InvalidOperationException: instance is read-only
      SetCulture2(th);
  
      th.Start();
  }
  
  public static void SetCulture1(System.Threading.Thread thread)
  {
      var ci = new System.Globalization.CultureInfo("pt-BR");
      ci.NumberFormat.CurrencyDecimalSeparator = ".";
  
      thread.CurrentCulture = ci; // <-- after this culture info not change
  
      if (thread.CurrentCulture.NumberFormat.CurrencyDecimalSeparator != ".")
      {
          Console.WriteLine("Nothing happened");
          Console.ReadKey();
      }
  }
  
  public static void SetCulture2(System.Threading.Thread thread)
  {
      thread.CurrentCulture = new System.Globalization.CultureInfo("pt-BR");
      thread.CurrentCulture.NumberFormat.CurrencyDecimalSeparator = "."; // <-- exception throws here
  }
  
  static void thread_test()
  {
      Console.WriteLine("Culture: {0}", CultureInfo.CurrentCulture.DisplayName);
  }
  

I notice that before .net 4.6 this sample works. Did something changed in 4.6?

Thank you!

Answer 1

While this odd situation has no answer (Microsoft bug report), I found a work around setting DefaultThreadCurrentCulture at the start of my code (Main method):

        var ci = new System.Globalization.CultureInfo(System.Globalization.CultureInfo.CurrentCulture.LCID);
        ci.NumberFormat.CurrencyDecimalSeparator = ".";
        ci.NumberFormat.CurrencyGroupSeparator = ",";
        ci.NumberFormat.NumberDecimalSeparator = ".";
        ci.NumberFormat.NumberGroupSeparator = ",";
        ci.NumberFormat.PercentDecimalSeparator = ".";
        ci.NumberFormat.PercentGroupSeparator = ",";
        System.Globalization.CultureInfo.DefaultThreadCurrentCulture = ci;
        System.Globalization.CultureInfo.DefaultThreadCurrentUICulture = ci;