class Program
  {
    // тестовый пример по десериализации через ExtendedXmlSerializer
    static void Main()
    {
      string executableLocation = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
      string path = Path.Combine(executableLocation, "test.xml");

      using var fs = new FileStream(path, FileMode.Open);

      IExtendedXmlSerializer extendedXmlSerializer = new ConfigurationContainer()
        .UseAutoFormatting()
        .UseOptimizedNamespaces()
        .EnableImplicitTyping(typeof(CarCollection))
        .Create();

;

      XmlSerializer standartSerializer = new XmlSerializer(typeof(CarCollection));

      // стандартный сериализатор работает, расширенный нет
      var cars1 = standartSerializer.Deserialize(fs);

      fs.Seek(0, SeekOrigin.Begin);
      var cars2 = extendedXmlSerializer.Deserialize<CarCollection>(fs);
    }
  }