using System.Globalization;
public static void Main()
Console.WriteLine(a.ToString("#,###.###", CultureInfo.CreateSpecificCulture("en-US")));
Console.WriteLine(b.ToString("#,###.###", CultureInfo.CreateSpecificCulture("en-US")));
Console.WriteLine(a.ToString("#,###.###", CultureInfo.CreateSpecificCulture("de-DE")));
Console.WriteLine(b.ToString("#,###.###", CultureInfo.CreateSpecificCulture("de-DE")));