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本文主要是對枚舉-enum相關(guān)知識的總結(jié)

C#中除了簡單的變量類型外，還提供了三種較為復(fù)雜的變量類型，包括枚舉、結(jié)構(gòu)和數(shù)組。本文主要講述枚舉相關(guān)的知識。

枚舉類型（也稱為枚舉），提供了一種有效的方式，來定義可能分配給變量的一組已命名的整數(shù)常量，使用enum關(guān)鍵字聲明。

默認(rèn)情況下，第一個枚舉數(shù)的值為0，之后每個連續(xù)枚舉數(shù)的值加1；若設(shè)置某一枚舉數(shù)的值，之后的枚舉數(shù)仍然按1遞增。示例如下：

        enum Day
        {
            Sunday,
            Monday,
            Tuesday,
            Wednesday,
            Thursday,
            Friday,
            Saturday
        };

        enum Number
        {
            One = 1,
            Two,
            Three,
            Eleven = 11,
            Twelve,
            Thirteen
        };

枚舉中每個元素的基礎(chǔ)類型都是int，可以使用冒號指明另一種整數(shù)類型。已批準(zhǔn)的枚舉類型有：byte、sbyte、short、ushort、int、uint、long、ulong

        enum Month : byte
        {
            January,
            February,
            March,
            April,
            May,
            June,
            July,
            August,
            September,
            October,
            November,
            December
        };

枚舉類型的枚舉器列表中元素可以分配為任何值，同時也可以使用計算值

        enum MachineState
        {
            PowerOff = 0,
            Running = 5,
            Sleeping = 10,
            Hibernating = Sleeping + 5
        }

枚舉相關(guān)的轉(zhuǎn)換：

1.轉(zhuǎn)換成整數(shù)

            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}");

輸出：

2.轉(zhuǎn)換成字符串

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

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

輸出：

3.從字符串中獲取枚舉值

Enum.Parse()靜態(tài)方法，帶有3個參數(shù)。第一個參數(shù)是要使用的枚舉類型，其語法是關(guān)鍵字typeof后跟放在括號中的枚舉類名；第二個參數(shù)是要轉(zhuǎn)換的字符串；第三個參數(shù)是一個bool值，指定在進(jìn)行轉(zhuǎn)換時是否忽略大小寫。

            string todayData = "Wednesday";
            Day dayData = (Day)Enum.Parse(typeof(Day), todayData, true);
            Console.WriteLine($"Enum.Parse()方法：{dayData}");

輸出：

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

            string name = Enum.GetName(typeof(Day), 3);
            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();

輸出：

枚舉類型作為位標(biāo)志：定義枚舉時，添加Flags特性，之后便可以對這些值執(zhí)行AND、OR、NOT、XOR按位運算

        [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(&):判斷是否包含該值；OR(|):組合；NOT(~):取反；XOR(^):去除其中一個值

            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");

輸出：

注釋掉[Flags]后，輸出內(nèi)容為：

參考文章：

http://www.rzrgm.cn/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

posted on 2018-01-31 14:18 雪溪閱讀(15231) 評論(0) 收藏舉報

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