C# 之门课程系列-10

枚举的概述

枚举是程序员定义的数据类型，与类或结构类似

• 与结构一样是值类型
• 枚举只有一种类型成员：命名的整数值常量

 private enum Result
        {
             Success,
             Fail
        }

豆号分隔，不是分号，每个枚举类型都有一个底层整数类型，默认是int

输出试一下

 private enum TrafficLight
        {
            Red,
            Yellow,
            Green
        }


        static void Main()
        {
            TrafficLight t1 = TrafficLight.Red;
            TrafficLight t2 = TrafficLight.Yellow;
            TrafficLight t3 = TrafficLight.Green;
            Console.WriteLine("T1:{0}\t{1}", t1, (int)t1);
            Console.WriteLine("T2:{0}\t{1}", t2, (int)t2);
            Console.WriteLine("T3:{0}\t{1}", t3, (int)t3);
            Console.ReadKey();
        }

显式值

可以显示声明一个枚举对应的值，这个在有些地方可以用到，比如权限枚举表

 private enum Limited
        {
            System=10,
            User=20,
            Material=30,
            Dashboard=40,
            Report=50
        }

这样设置至少有一个好处，可以在未来项目发生变更时，System下增中一个日志模块，我们就可以用Log=11

Flags标志位

 [Flags]
        private enum Light
        {
            black=0x00,
            Red = 0x01,
            Yellow = 0x02,
            Green = 0x04
        }

        static void Main()
        {
            Light l1 = Light.Red;
            Light l2 = Light.Yellow;
            Light l3 = Light.Green;

            Console.WriteLine(l1 & l2); ;

            Console.ReadKey();
        }

Flags 特性不会改变计算结果，不仅可以单独的值，还可以按位求标志进行组合

下面是枚举常用的工具类

 #region 枚举成员转成dictionary类型
        /// <summary>
        /// 转成dictionary类型
        /// </summary>
        /// <param name="enumType"></param>
        /// <returns></returns>
        public static Dictionary<int, string> EnumToDictionary(this Type enumType)
        {
            Dictionary<int, string> dictionary = new Dictionary<int, string>();
            Type typeDescription = typeof(DescriptionAttribute);
            FieldInfo[] fields = enumType.GetFields();
            int sValue = 0;
            string sText = string.Empty;
            foreach (FieldInfo field in fields)
            {
                if (field.FieldType.IsEnum)
                {
                    sValue = ((int)enumType.InvokeMember(field.Name, BindingFlags.GetField, null, null, null));
                    object[] arr = field.GetCustomAttributes(typeDescription, true);
                    if (arr.Length > 0)
                    {
                        DescriptionAttribute da = (DescriptionAttribute)arr[0];
                        sText = da.Description;
                    }
                    else
                    {
                        sText = field.Name;
                    }
                    dictionary.Add(sValue, sText);
                }
            }
            return dictionary;
        }
        /// <summary>
        /// 枚举成员转成键值对Json字符串
        /// </summary>
        /// <param name="enumType"></param>
        /// <returns></returns>
        public static string EnumToDictionaryString(this Type enumType)
        {
            List<KeyValuePair<int, string>> dictionaryList = EnumToDictionary(enumType).ToList();
            var sJson = JsonConvert.SerializeObject(dictionaryList);
            return sJson;
        }
        #endregion

        #region 获取枚举的描述
        /// <summary>
        /// 获取枚举值对应的描述
        /// </summary>
        /// <param name="enumType"></param>
        /// <returns></returns>
        public static string GetDescription(this System.Enum enumType)
        {
            FieldInfo EnumInfo = enumType.GetType().GetField(enumType.ToString());
            if (EnumInfo != null)
            {
                DescriptionAttribute[] EnumAttributes = (DescriptionAttribute[])EnumInfo.GetCustomAttributes(typeof(DescriptionAttribute), false);
                if (EnumAttributes.Length > 0)
                {
                    return EnumAttributes[0].Description;
                }
            }
            return enumType.ToString();
        }
        #endregion

        #region 根据值获取枚举的描述
        public static string GetDescriptionByEnum<T>(this object obj)
        {
            var tEnum = System.Enum.Parse(typeof(T), obj.ParseToString()) as System.Enum;
            var description = tEnum.GetDescription();
            return description;
        }
        #endregion