你必须知道的.NET之特性和属性(3)

[AttributeUsage(AttributeTargets.Class |
AttributeTargets.Method,
Inherited = true)]
public class TestAttribute : System.Attribute
{
public TestAttribute(string message)
{
throw new Exception("error:" + message);
}
public void RunTest()
{
Console.WriteLine("TestAttribute here.");
}
}

[Test("Error Here.")]
public void CannotRun()
{
//
}

public static void Main(string[] args)
{
Tester t = new Tester();
t.CannotRun();
Type tp = typeof(Tester);
TestAttribute myAtt = (TestAttribute)Attribute.GetCustomAttribute((MemberInfo)tp, 
typeof(TestAttribute));
}

using System;
using System.Reflection;  //应用反射技术获得特性信息
namespace Anytao.net
{
//定制特性也可以应用在其他定制特性上，
//应用AttributeUsage，来控制如何应用新定义的特性
[AttributeUsageAttribute(AttributeTargets.All,       //可应用任何元素
AllowMultiple = true,                            //允许应用多次
Inherited = false)]                              //不继承到派生类
//特性也是一个类，
//必须继承自System.Attribute类，
//命名规范为："类名"+Attribute。        
public class MyselfAttribute : System.Attribute
{
//定义字段
private string _name;
private int _age;
private string _memo;
//必须定义其构造函数，如果不定义有编译器提供无参默认构造函数
public MyselfAttribute()
{
}
public MyselfAttribute(string name, int age)
{
_name = name;
_age = age;
}
//定义属性
//显然特性和属性不是一回事儿
public string Name
{
get { return _name == null ? string.Empty : _name; }
}
public int Age
{
get { return _age; }
}
public string Memo
{
get { return _memo; }
set { _memo = value; }
}
//定义方法
public void ShowName()
{
Console.WriteLine("Hello, {0}", _name == null ? "world." : _name);
}
}
//应用自定义特性
//可以以Myself或者MyselfAttribute作为特性名
//可以给属性Memo赋值
[Myself("Emma", 25, Memo = "Emma is my good girl.")]
public class Mytest
{
public void SayHello()
{
Console.WriteLine("Hello, my.net world.");
}
}
public class Myrun
{
public static void Main(string[] args)
{
//如何以反射确定特性信息
Type tp = typeof(Mytest);
MemberInfo info = tp;
MyselfAttribute myAttribute =
(MyselfAttribute)Attribute.GetCustomAttribute(info, 
typeof(MyselfAttribute));
if (myAttribute != null)
{
//嘿嘿，在运行时查看注释内容，是不是很爽
Console.WriteLine("Name: {0}", myAttribute.Name);
Console.WriteLine("Age: {0}", myAttribute.Age);
Console.WriteLine("Memo of {0} is {1}", myAttribute.Name, 
myAttribute.Memo);
myAttribute.ShowName();
}
//多点反射
object obj = Activator.CreateInstance(typeof(Mytest));
MethodInfo mi = tp.GetMethod("SayHello");
mi.Invoke(obj, null);
Console.ReadLine();
}
}
}