using System;

using System.Linq;

​

namespace Example

{

    public enum General : int

    {

        One = 0,

        Two = 1,

        Three = 2,

        Four = 4,

        Five = 8

    }

​

    public enum A : int

    {

        One = General.One,

        Two = General.Two,

        Three = General.Three,

        Four = General.Four,

    }

​

    public enum B : int

    {

        Three = General.Three,

        Four = General.Four,

        Five = General.Five

    }

​

    public enum C : int

    {

        One = General.One,

        Three = General.Three,

        Five = General.Five

    }

​

    static public class ExtensionMethods

    {

        static public General ToGeneral<T>(this T input) where T : struct, IConvertible

        {

            if (!typeof(T).IsEnum) throw new ArgumentException("Input must be an enum.");

            return (General)((int)(object)input & Enum.GetValues(typeof(General)).Cast<int>().Sum());

        }

        static public T ToEnum<T>(this General input)

        {

            if (!typeof(T).IsEnum) throw new ArgumentException("Output type must be an enum.");

​

            return (T)Enum.ToObject(typeof(T), (int)input & Enum.GetValues(typeof(T)).Cast<int>().Sum());

        }

    }

    public class Program

    {

        static public TOut Convert<TIn,TOut>(TIn input) where TIn : struct, IConvertible where TOut: struct, IConvertible

        {

            var general = input.ToGeneral();

            return general.ToEnum<TOut>();

        }

        public static void Main()

        {

            A valAsA = A.One | A.Three | A.Four;

            B valAsB = Convert<A,B>(valAsA);  // Should give me "B.Three | B.Four"

            C valAsC = Convert<A,C>(valAsA); // Should give me "C.One | C.Three"

            Console.WriteLine("{0} should equal {1}", valAsB, (B.Three | B.Four));

            Console.WriteLine("{0} should equal {1}", valAsC, (C.One | C.Three));

        }

    }

}