ahjesus C# Flags 位域略说

class Program {

    [Flags]

    public enum Week {

        [Description("星期一")]

        Monday = 1 << 0,//1

        [Description("星期二")]

        Tuesday = 1 << 1,//2

        [Description("星期三")]

        Wednesday = 1 << 2,//4

        [Description("星期四")]

        Tursday = 1 << 3,//8

        [Description("星期五")]

        Friday = 1 << 4,//16

        [Description("星期六")]

        Saturday = 1 << 5,//32

        [Description("星期日")]

        Sunday = 1 << 6//64

    }



    static void Main(string[] args) {

        //1.|表示两边求并集（元素相加，相同元素只出现一次）

        Week week = Week.Wednesday | Week.Monday | Week.Monday | Week.Tuesday;//Monday,Tuesday,Wednesday 

            

        //2.&表示两边是否其中一个是另外一个的子集，如果是返回子集，否则返回0

        //week = Week.Monday & week;//Monday

        //week = (Week.Sunday | Week.Monday | Week.Tuesday) & week;//Monday,Tuesday

        //week = Week.Sunday & week;//0

        //出自http://www.cnblogs.com/ahjesus 尊重作者辛苦劳动成果，转载请注明出处，谢谢！

        //3.^表示从两者的并集中去除两者的交集

        //week = Week.Monday ^ Week.Monday;//0

        //week = (Week.Monday | Week.Tuesday) ^ (Week.Tuesday | Week.Wednesday);//Monday,Wednesday



        //4.~表示取补,按二进制每4位一组，不足4位最左边补0，然后1变0,0变1，用法主要和&一起使用去除其中的某个元素

        //week = ~Week.Wednesday;//-5

        //week = week & (~Week.Monday); //Monday,Tuesday



        //存入数据库可以转换为int,从数据库中读出来可以转换为枚举

        //week = Week.Monday  | Week.Tuesday;

        //int i = (int)week;//3

        //week = (Week)Enum.Parse(typeof(Week), "3");//Monday,Tuesday





        NameValueCollection nvc = GetNVCFromEnumValue(typeof(Week));

        foreach (string key in nvc.AllKeys)

        {

            Console.WriteLine(key + ":" + nvc[key]);

        }

            

        Console.ReadKey();

    }



    /// < summary>  

    /// 从枚举类型和它的特性读出并返回一个键值对  

    /// < /summary>  

    /// < param name="enumType">Type,该参数的格式为typeof(需要读的枚举类型)< /param>  

    /// < returns>键值对< /returns>  

    public static NameValueCollection GetNVCFromEnumValue(Type enumType) {

        NameValueCollection nvc = new NameValueCollection();

        Type typeDescription = typeof(DescriptionAttribute);

        System.Reflection.FieldInfo[] fields = enumType.GetFields();

        string strText = string.Empty;

        string strValue = string.Empty;

        foreach (FieldInfo field in fields) {

            if (field.FieldType.IsEnum) {

                strValue = ((int)enumType.InvokeMember(field.Name, BindingFlags.GetField, null, null, null)).ToString();

                object[] arr = field.GetCustomAttributes(typeDescription, true);

                if (arr.Length > 0) {//出自http://www.cnblogs.com/ahjesus 尊重作者辛苦劳动成果，转载请注明出处，谢谢！

                    DescriptionAttribute aa = (DescriptionAttribute)arr[0];

                    strText = aa.Description;

                }

                else {

                    strText = field.Name;

                }

                nvc.Add(strText, strValue);

            }

        }

        return nvc;

    } 

}