Enum常用方法

１.　enum 通常定义在namespace 中，这样，所有在这个namespace下的类都可以访问这个enum。
enum 也可以定义在class 或struct 中。

2. Enum常与switch连用
3. 枚举格式字符串

Console.WriteLine(ConsoleColor.Red.ToString(“G”)); // Displays Red
Console.WriteLine(ConsoleColor.Red.ToString(“D”)); //十进制
Console.WriteLine(ConsoleColor.Red.ToString(“F”)); // Displays Red
Console.WriteLine(ConsoleColor.Red.ToString(“X”)); //displays hex

3. 代码示例

using System;
using System.Collections.Generic;
using System.Linq.Expressions;

namespace testEnum
{
    public enum EAlarmType : uint
    {
        Null = 0,
        Common = 1,
        Warn = 2,
        Serious = 3,

    }
    public enum MsgDetails : uint
    {
        Null = 0,
        PLC_Error = 1, 
        GPIO_Error = 2, 
        PC_PowerOff = 3,
        Reader_Error = 4 
    }
    public class EnumComparer : IEqualityComparer where T : struct
    {
        public bool Equals(T first, T second)
        {
            var firstPara = Expression.Parameter(typeof(T), "first");
            var secondPara = Expression.Parameter(typeof(T), "second");
            var equalExpression = Expression.Equal(firstPara, secondPara);

            return Expression.Lambda>(equalExpression, new[] { firstPara, secondPara }).Compile().Invoke(first, second);
        }
        public int GetHashCode(T instance)
        {
            var parameter = Expression.Parameter(typeof(T), "instance");
            var convertExpression = Expression.Convert(parameter, typeof(int));

            return Expression.Lambda>(convertExpression, new[] { parameter }).Compile().Invoke(instance);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            //获取枚举项的名字---Enum.GetName//
            string getname = Enum.GetName(typeof(MsgDetails), MsgDetails.GPIO_Error);

            Console.WriteLine("{0}--{1}",MsgDetails.GPIO_Error,getname);
            //将string/常量值--转为枚举项  Enum.Parse
            MsgDetails msgMember = (MsgDetails)Enum.Parse(typeof(MsgDetails), getname);

            ///获取枚举项对应的常量值
            int value = (int)MsgDetails.PLC_Error;
            Console.WriteLine("{0}--{1}",MsgDetails.PLC_Error,value);

            //依据常量值获取枚举中对应项---Enum.ToObject
            MsgDetails fhkg = (MsgDetails)Enum.ToObject(typeof(MsgDetails), value);

            //判断枚举中是否包含某一项-- Enum.IsDefined
            bool IsDefined = Enum.IsDefined(typeof(MsgDetails), getname);
            Console.WriteLine(IsDefined);


            //Enum类型没有实现IEquatable接口，Dictionary中无法添加Enum类型的元素
            Dictionary dic = new Dictionary();
            dic.Add(Enum.GetName(typeof(MsgDetails), MsgDetails.GPIO_Error), "common");
            dic.Add(Enum.GetName(typeof(MsgDetails), MsgDetails.PLC_Error), "servier");

            //MsgDetails.PLC_Error.ToString()--- Enum.GetName(typeof(MsgDetails), MsgDetails.GPIO_Error)都可以获取常量值对应的名字
            string etype = dic[ Enum.GetName(typeof(MsgDetails), MsgDetails.GPIO_Error)];
           
            Console.WriteLine("key--{0}, value--{1}",MsgDetails.GPIO_Error, etype);
            Console.WriteLine("Key--{0},value--{1}", MsgDetails.PLC_Error, dic[MsgDetails.PLC_Error.ToString()]);

            //通过实现Enum的IEquatable接口，便可以将enum类型作为key 添加到dictionary中
            var dicT = new Dictionary(new EnumComparer());
            dicT.Add(MsgDetails.GPIO_Error, EAlarmType.Common);
            dicT.Add(MsgDetails.PC_PowerOff, EAlarmType.Serious);
            dicT.Add(MsgDetails.PLC_Error, EAlarmType.Common);
            
            //获取dictionary中key对应的value值
            EAlarmType type = dicT[MsgDetails.PC_PowerOff];
            Console.WriteLine(type);

            Console.ReadLine();


        }
    }

   
}