示例: 扩展方法

using System;
using System.IO;

namespace EnumTest1
{
    class Program
    {
        static void Main(string[] args)
        {
            FileAttributes fa = FileAttributes.System;
            fa = fa.Set(FileAttributes.ReadOnly);
            fa = fa.Clear(FileAttributes.System);
            fa.ForEach(f=>Console.WriteLine(f));

            Console.ReadLine();
        }
    }

    internal static class FileAttributesExtensionMethods
    {
        public static Boolean IsSet(this FileAttributes flags, FileAttributes flagToTest)
        {
            if (flagToTest == 0)
                throw new ArgumentOutOfRangeException("flagToTest", "Value must not be 0");
            return (flags & flagToTest) == flagToTest;
        }

        public static Boolean IsClear(this FileAttributes flags, FileAttributes flagToTest)
        {
            if(flagToTest == 0)
                throw new ArgumentOutOfRangeException("flagToTest", "Value must not be 0");
            return !IsSet(flags, flagToTest);
        }

        public static Boolean AnyFlagsSet(this FileAttributes flags, FileAttributes testFlags)
        {
            return (flags & testFlags) != 0;
        }

        public static FileAttributes Set(this FileAttributes flags, FileAttributes setFlags)
        {
            return flags | setFlags;
        }

        public static FileAttributes Clear(this FileAttributes flags, FileAttributes clearFlags)
        {
            return flags & ~clearFlags;
        }

        public static void ForEach(this FileAttributes flags, Action<FileAttributes> processFlag)
        {
            if (processFlag == null)
                throw new ArgumentNullException("processFlag");
            for(UInt32 bit = 1; bit != 0; bit <<= 1)
            {
                UInt32 temp = ((UInt32)flags) & bit;
                if (temp != 0)
                    processFlag((FileAttributes)temp);
            }
        }
    }
}

运行测试