C# enum枚举知识总结

C#中除了简单的变量类型外，还提供了三种较为复杂的变量类型，包括枚举、结构和数组。本文主要讲述枚举相关的知识。

枚举类型（也称为枚举），提供了一种有效的方式，来定义可能分配给变量的一组已命名的整数常量，使用enum关键字声明。

默认情况下，第一个枚举数的值为0，之后每个连续枚举数的值加1；若设置某一枚举数的值，之后的枚举数仍然按1递增。示例如下：

        enum Day

        {

            Sunday,

            Monday,

            Tuesday,

            Wednesday,

            Thursday,

            Friday,

            Saturday

        };

        enum Number

        {

            One = ,

            Two,

            Three,

            Eleven = ,

            Twelve,

            Thirteen

        };

枚举中每个元素的基础类型都是int，可以使用冒号指明另一种整数类型。已批准的枚举类型有：byte、sbyte、short、ushort、int、uint、long、ulong

        enum Month : byte

        {

            January,

            February,

            March,

            April,

            May,

            June,

            July,

            August,

            September,

            October,

            November,

            December

        };

枚举类型的枚举器列表中元素可以分配为任何值，同时也可以使用计算值

        enum MachineState

        {

            PowerOff = ,

            Running = ,

            Sleeping = ,

            Hibernating = Sleeping +

        }

枚举相关的转换：

1.转换成整数

            Day today = Day.Wednesday;

            Console.WriteLine($"today is {today}");

            int dayNumber = (int)today;

            Console.WriteLine($"{today} is day number {dayNumber}");

             Month month = Month.January;

            byte monthNumber = (byte)month;

            Console.WriteLine($"{month} is month number {monthNumber}");

输出：

2.转换成字符串

            string todayString = Convert.ToString(today);

            Console.WriteLine($"Convert.ToString()方式： {todayString}");

            string todayString2 = today.ToString();

            Console.WriteLine($".ToString()方式：{todayString2}");

输出：

3.从字符串中获取枚举值

Enum.Parse()静态方法，带有3个参数。第一个参数是要使用的枚举类型，其语法是关键字typeof后跟放在括号中的枚举类名；第二个参数是要转换的字符串；第三个参数是一个bool值，指定在进行转换时是否忽略大小写。

            string todayData = "Wednesday";

            Day dayData = (Day)Enum.Parse(typeof(Day), todayData, true);

            Console.WriteLine($"Enum.Parse()方法：{dayData}");

输出：

3个方法： Enum.GetName() 、Enum.GetNames()、Enum.GetValues()

            string name = Enum.GetName(typeof(Day), );

            Console.WriteLine(name);

            Console.WriteLine("The names of the Day Enum are:");

            foreach (string str in Enum.GetNames(typeof(Day)))

                Console.Write(str + " ");

            Console.WriteLine();

            Console.WriteLine("The values of the Day Enum are:");

            foreach (int value in Enum.GetValues(typeof(Day)))

                Console.Write(value + " ");

            Console.WriteLine();

输出：

枚举类型作为位标志：定义枚举时，添加Flags特性，之后便可以对这些值执行AND、OR、NOT、XOR按位运算

        [Flags]

        enum WeekDay

        {

            None = 0x00,       //0000 0000

            Sunday = 0x01,     //0000 0001

            Monday = 0x02,     //0000 0010

            Tuesday = 0x04,    //0000 0100

            Wednesday = 0x08,  //0000 1000

            Thursday = 0x10,   //0001 0000

            Friday = 0x20,     //0010 0000

            Saturday = 0x40    //0100 0000

        };

        [Flags]

        public enum CarOptions

        {

            // The flag for SunRoof is 0001.

            SunRoof = 0x01,

            // The flag for Spoiler is 0010.

            Spoiler = 0x02,

            // The flag for FogLights is 0100.

            FogLights = 0x04,

            // The flag for TintedWindows is 1000.

            TintedWindows = 0x08,

        }

AND(&):判断是否包含该值；OR(|):组合；NOT(~):取反；XOR(^):去除其中一个值

            CarOptions options = CarOptions.SunRoof | CarOptions.FogLights;

            Console.WriteLine(options);

            Console.WriteLine((int)options);

            WeekDay meetingDays = WeekDay.Tuesday | WeekDay.Thursday;

            meetingDays = meetingDays | WeekDay.Friday;

            Console.WriteLine("Meeting days are {0}", meetingDays);

            meetingDays = meetingDays ^ WeekDay.Tuesday;

            Console.WriteLine("Meeting days are {0}", meetingDays);

            bool test = (meetingDays & WeekDay.Thursday) == WeekDay.Thursday;

            Console.WriteLine("Thursday {0} a meeting day.", test == true ? "is" : "is not");

输出：

注释掉[Flags]后，输出内容为：

参考文章：

https://www.cnblogs.com/williamwsj/p/6047884.html

https://docs.microsoft.com/zh-cn/dotnet/csharp/language-reference/keywords/enum

https://docs.microsoft.com/zh-cn/dotnet/csharp/programming-guide/enumeration-types

巴特西

C# enum枚举知识总结

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