C# 中 enum的总结

http://apps.hi.baidu.com/share/detail/23749270

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); } }