Enumeration

using System;
using System.Collections.Generic;
using System.Text;


class Program
{
    //Flag enums are designed to support bitwise operations on the enum values
    [Flags]
    public enum LogLevels : uint
    {
        //Increment by powers of 2.
        //If you don't assign explicit values VS increments by 1. 
        None        = 0,
        NotifyTrace = 1,
        NotifyDebug = 2,
        NotifyInfo  = 4,
        NotifyWarn  = 8,
        NotifyError = 16,
        NotifyAll   =   NotifyTrace | NotifyDebug | NotifyInfo | NotifyWarn | NotifyError,
        //The rationale for avoiding zero in a flag enumeration for an actual flag 
        //is that you can't OR it in with other flags as expected.
        NotifyNone  = ~(NotifyTrace | NotifyDebug | NotifyInfo | NotifyWarn | NotifyError),
    }

    LogLevels options = LogLevels.NotifyDebug | LogLevels.NotifyWarn | LogLevels.NotifyError;

    static void Main(string[] args)
    {
        Program p = new Program();
        p.Test1();
        p.Test2();
        LogLevels v = (LogLevels) 2;
        p.Test3(v);

        // Interesting, Compiler Catch Invalid Argument
        p.Test4(2);
        // Surprise, Correct
        p.Test4(0);

        Console.ReadLine();
    }

    public void Test1()
    {
        Type value = typeof(LogLevels);
        foreach (string s in Enum.GetNames(value))
        {
            Console.WriteLine("{0,-11} = {1}", s, Enum.Format(value, Enum.Parse(value, s), "d"));
        }
    }

    public void Test2()
    {
        Console.WriteLine(IsLevelsSet(LogLevels.NotifyNone));
        Console.WriteLine(IsLevelsSet(LogLevels.NotifyTrace));
        Console.WriteLine(IsLevelsSet(LogLevels.NotifyDebug));
        Console.WriteLine(IsLevelsSet(LogLevels.NotifyInfo));
        Console.WriteLine(IsLevelsSet(LogLevels.NotifyWarn));
        Console.WriteLine(IsLevelsSet(LogLevels.NotifyError));
        Console.WriteLine(IsLevelsSet(LogLevels.NotifyAll));
    }

   
    public void Test3(LogLevels value)
    {
        switch (value)
        {
            case LogLevels.NotifyTrace:
                Console.WriteLine(value.ToString());
                break;
            case LogLevels.NotifyDebug:
                Console.WriteLine(value.ToString());
                break;
            case LogLevels.NotifyInfo:
                Console.WriteLine(value.ToString());
                break;
            case LogLevels.NotifyWarn:
                Console.WriteLine(value.ToString());
                break;
            case LogLevels.NotifyError:
                Console.WriteLine(value.ToString());
                break;
            case LogLevels.NotifyAll:
                Console.WriteLine(value.ToString());
                break;
            case LogLevels.NotifyNone:
                Console.WriteLine(value.ToString());
                break;
            default:
                break;
        }
    }

    public void Test4(LogLevels value)
    {
        //in C# the literal constant 0 implicitly converts to any enum type             
        if (value == LogLevels.None)
            Console.WriteLine(value.ToString());
    }

    private bool IsLevelsSet(LogLevels values)
    {
        return (options & values) == values;
    }

}