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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);
}
}

[整理自网络]

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