关于enum应用的总结

1、关于enum的定义

/// <summary>

/// 新闻、下载资源等的审核状态

/// </summary>

public enum ApplyStatus

{

/// <summary>

/// 审核不通过

/// </summary>

NotPassed = -1,

/// <summary>

/// 未审核

/// </summary>

NotApply = 0,

/// <summary>

/// 审核通过

/// </summary>

Passed = 1

}
2、符号名和常数值的互相转换

ApplyStatus status = ApplyStatus.NotApply;

int fabNum = (int)status;//转换为常数值。必须使用强制转换。

ApplyStatus statusString = (ApplyStatus)1;//常数值转换成符号名。如果使用ToString()，则是((ApplyStatus)1).ToString()，注意必须有括号。

string applyType = status.ToString();//显示符号名

string applyVal = status.ToString("D");//显示常数值
3、获得所有符号名的方法（具体参见Enum类）

foreach (string s in Enum.GetNames(typeof(ApplyStatus)))

{

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);

}

}