• C#中enum的总结(转载)


    1、关于enum的定义
    enum Fabric
    {
    Cotton = 1,
    Silk = 2,
    Wool = 4,
    Rayon = 8,
    Other = 128
    }
    2、符号名和常数值的互相转换
     
                Fabric fab = Fabric.Cotton;
                int fabNum = (int)fab;//转换为常数值。必须使用强制转换。
                Fabric fabString = (Fabric)1;//常数值转换成符号名。如果使用ToString(),则是((Fabric)1).ToString(),注意必须有括号。

                string fabType = fab.ToString();//显示符号名
                string fabVal = fab.ToString ("D");//显示常数值
     
    3、获得所有符号名的方法(具体参见Enum类)
     
            public enum MyFamily
            {
                YANGZHIPING = 1,
                GUANGUIQIN = 2,
                YANGHAORAN = 4,
                LIWEI = 8,
                GUANGUIZHI = 16,
                LISIWEN = 32, 
                LISIHUA = 64,
            }
     
                foreach (string s in Enum.GetNames(typeof(MyFamily)))
                {
                    Console.WriteLine(s);
                }
     
    4、将枚举作为位标志来处理
    根据下面的两个例子,粗略地说,一方面,设置标志[Flags]或者[FlagsAttribute],则表明要将符号名列举出来;另一方面,可以通过强制转换,将数字转换为符号名。说不准确。看下面的例子体会吧。注意:
              例一:
              Fabric fab = Fabric.Cotton | Fabric.Rayon | Fabric.Silk;
              Console.WriteLine("MyFabric = {0}", fab);//输出:Fabric.Cotton | Fabric.Rayon | Fabric.Silk;
    例二:
    class FlagsAttributeDemo
    {
        // Define an Enum without FlagsAttribute.
        enum SingleHue : short
        {
            Black = 0,
            Red = 1,
            Green = 2,
            Blue = 4
        };

        // Define an Enum with FlagsAttribute.
        [FlagsAttribute] 
        enum MultiHue : short
        {
            Black = 0,
            Red = 1,
            Green = 2,
            Blue = 4
        };

        static void Main( ) 
        {
            Console.WriteLine( 
                "This example of the FlagsAttribute attribute /n" +
                "generates the following output." );
            Console.WriteLine( 
                "/nAll possible combinations of values of an /n" + 
                "Enum without FlagsAttribute:/n" );
            
            // Display all possible combinations of values.
            for( int val = 0; val <= 8; val++ )
                Console.WriteLine( "{0,3} - {1}",  val, ( (SingleHue)val ).ToString( ) );

            Console.WriteLine(  "/nAll possible combinations of values of an /n" + "Enum with FlagsAttribute:/n" ); 
            
            // Display all possible combinations of values.
            // Also display an invalid value.
            for( int val = 0; val <= 8; val++ )
                Console.WriteLine ( "{0,3} - {1}",  val, ( (MultiHue)val ).ToString( ) );
        } 


    /*
    This example of the FlagsAttribute attribute
    generates the following output.

    All possible combinations of values of an 
    Enum without FlagsAttribute:

      0 - Black
      1 - Red
      2 - Green
      3 - 3
      4 - Blue
      5 - 5
      6 - 6
      7 - 7
      8 - 8

    All possible combinations of values of an
    Enum with FlagsAttribute: 

      0 - Black
      1 - Red
      2 - Green
      3 - Red, Green
      4 - Blue
      5 - Red, Blue
      6 - Green, Blue
      7 - Red, Green, Blue
      8 - 8
    */
    5、枚举作为函数参数。经常和switch结合起来使用。下面举例

            public static double GetPrice(Fabric fab)
            {
                switch (fab)
                {
                    case Fabric.Cotton: return (3.55);
                    case Fabric.Silk: return (5.65);
                    case Fabric.Wool: return (4.05);
                    case Fabric.Rayon: return (3.20);
                    case Fabric.Other: return (2.50);
                    default: return (0.0);
                }
            }

    6、上面三点一个完整的例子

            //1、enum的定义
            public enum Fabric : short
            {
                Cotton = 1,
                Silk = 2,
                Wool = 3,
                Rayon = 8,
                Other = 128
            }

            //将枚举作为参数传递
            public static double GetPrice(Fabric fab)
            {
                switch (fab)
                {
                    case Fabric.Cotton: return (3.55);
                    case Fabric.Silk : return (5.65);
                    case Fabric.Wool: return (4.05);
                    case Fabric.Rayon: return (3.20);
                    case Fabric.Other: return (2.50);
                    default: return (0.0);
                } 
            }

            public static void Main()
            {
                Fabric fab = Fabric.Cotton;
                int fabNum = (int)fab;
                string fabType = fab.ToString();
                string fabVal = fab.ToString ("D");
                double cost = GetPrice(fab);
                Console.WriteLine("fabNum = {0}/nfabType = {1}/nfabVal = {2}/n", fabNum, fabType, fabVal);
                Console.WriteLine("cost = {0}", cost); 
            }

    7、Enum类的使用

    Enum.IsDefinde、Enum.Parse两种方法经常一起使用,来确定一个值或符号是否是一个枚举的成员,然后创建一个实例。Enum.GetName打印出一个成员的值;Enum.GetNames打印出所有成员的值。其中注意typeof的使用。这一点很重要。

            public enum MyFamily
            {
                YANGZHIPING = 1,
                GUANGUIQIN = 2,
                YANGHAORAN = 4,
                LIWEI = 8,
                GUANGUIZHI = 16,
                LISIWEN = 32, 
                LISIHUA = 64,
            }

                string s = "YANGHAORAN";
                if (Enum.IsDefined(typeof(MyFamily), s))
                {
                    MyFamily f = (MyFamily)Enum.Parse(typeof(MyFamily), s);
                    GetMyFamily(f);
                    Console.WriteLine("The name is:" + Enum. GetName(typeof(MyFamily), 2));
                    string[] sa = Enum.GetNames(typeof(MyFamily)); 
                    foreach (string ss in sa)
                    {
                        Console.WriteLine(ss);
                    }
                }

    MSDN解释:http://msdn.microsoft.com/zh-cn/library/sbbt4032%28VS.80%29.aspx

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  • 原文地址:https://www.cnblogs.com/stevenjson/p/3658555.html
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