C# 中 enum的总结

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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);                 }             }