yes.cs

    public class Program
    {
        public enum MyEnum { Ready, Set, Go, Stop }

        public static List<Enum> MyEnums = new List<Enum>();
        public static List<CustomClass> MyClass = new List<CustomClass>();

        static void Main(string[] args)
        {
            MyEnums.Add(MyEnum.Ready);
            //MyEnums.Add(MyEnum.Set);
            MyEnums.Add(MyEnum.Go);
            MyEnums.Add(MyEnum.Stop);

            MyClass.Add(new CustomClass(MyEnum.Ready, "Ready", "Ready!!"));
            //MyClass.Add(new CustomClass(MyEnum.Set, "Set", "Set!!"));
            MyClass.Add(new CustomClass(MyEnum.Go, "Go", "Go!!"));
            MyClass.Add(new CustomClass(MyEnum.Stop, "Stop", "Stop!!"));

            var matches = MyClass.Where(x => MyEnums.Contains(x.MyEnum));
            Console.WriteLine("matches: " + matches.Count());
            Console.ReadLine();
        }
    }