【转】C#中enum的总结

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);
                }
            }