C#基础学习系列之Attribute和反射详解

using System;
 
namespace AttTargsCS {
 // This attribute is only valid on a class.
 [AttributeUsage(AttributeTargets.Class)]
 public class ClassTargetAttribute : Attribute {
 }
 
 // This attribute is only valid on a method.
 [AttributeUsage(AttributeTargets.Method)]
 public class MethodTargetAttribute : Attribute {
 }
 
 // This attribute is only valid on a constructor.
 [AttributeUsage(AttributeTargets.Constructor)]
 public class ConstructorTargetAttribute : Attribute {
 }
 
 // This attribute is only valid on a field.
 [AttributeUsage(AttributeTargets.Field)]
 public class FieldTargetAttribute : Attribute {
 }
 
 // This attribute is valid on a class or a method.
 [AttributeUsage(AttributeTargets.Class|AttributeTargets.Method)]
 public class ClassMethodTargetAttribute : Attribute {
 }
 
 // This attribute is valid on a generic type parameter.
 [AttributeUsage(AttributeTargets.GenericParameter)]
 public class GenericParameterTargetAttribute : Attribute {
 }
 
 // This attribute is valid on any target.
 [AttributeUsage(AttributeTargets.All)]
 public class AllTargetsAttribute : Attribute {
 }
 
 [ClassTarget]
 [ClassMethodTarget]
 [AllTargets]
 public class TestClassAttribute {
  [ConstructorTarget]
  [AllTargets]
  TestClassAttribute() {
  }
 
  [MethodTarget]
  [ClassMethodTarget]
  [AllTargets]
  public void Method1() {
  }
 
  [FieldTarget]
  [AllTargets]
  public int myInt;
 
  public void GenericMethod<
   [GenericParameterTarget, AllTargets] T>(T x) {
  }
 
  static void Main(string[] args) {
  }
 }
}

[AttributeUsage(AttributeTargets.Class, AllowMultiple = true)] 
class MultiUseAttr : Attribute { } 
 
[MultiUseAttr, MultiUseAttr] 
class Class2 { } 

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method | 
    AttributeTargets.Property | AttributeTargets.Field, 
    Inherited = true)]
public class InheritedAttribute : Attribute
{}
 
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method |
    AttributeTargets.Property | AttributeTargets.Field, 
    Inherited = false)]
public class NotInheritedAttribute : Attribute
{} 
 
using System;
using System.Reflection;
 
[InheritedAttribute]
public class BaseA
{
 [InheritedAttribute] 
 public virtual void MethodA() 
 {}
}
 
public class DerivedA : BaseA
{
 public override void MethodA()
 {}
} 
 
[NotInheritedAttribute] 
public class BaseB
{
 [NotInheritedAttribute] 
 public virtual void MethodB() 
 {}
}
 
public class DerivedB : BaseB
{
 public override void MethodB()
 {}
}
 
public class Example
{
 public static void Main()
 {
  Type typeA = typeof(DerivedA);
  Console.WriteLine("DerivedA has Inherited attribute: {0}", 
      typeA.GetCustomAttributes(typeof(InheritedAttribute), true).Length > 0); 
  MethodInfo memberA = typeA.GetMethod("MethodA");
  Console.WriteLine("DerivedA.MemberA has Inherited attribute: {0}\n", 
      memberA.GetCustomAttributes(typeof(InheritedAttribute), true).Length > 0); 
 
  Type typeB = typeof(DerivedB);
  Console.WriteLine("DerivedB has Inherited attribute: {0}", 
      typeB.GetCustomAttributes(typeof(InheritedAttribute), true).Length > 0); 
  MethodInfo memberB = typeB.GetMethod("MethodB");
  Console.WriteLine("DerivedB.MemberB has Inherited attribute: {0}", 
      memberB.GetCustomAttributes(typeof(InheritedAttribute), true).Length > 0); 
 }
}
// The example displays the following output:
//  DerivedA has Inherited attribute: True
//  DerivedA.MemberA has Inherited attribute: True
//  
//  DerivedB has Inherited attribute: False
//  DerivedB.MemberB has Inherited attribute: False

System.Reflection.Assembly
System.Reflection.MemberInfo
System.Reflection.EventInfo
System.Reflection.FieldInfo
System.Reflection.MethodBase
System.Reflection.ConstructorInfo
System.Reflection.MethodInfo
System.Reflection.PropertyInfo
System.Type

public void Process(object processObj)
{
Type t = processsObj.GetType();
if(t.GetInterface(“ITest”) !=null)
     …
}

public class TestClass {
   private string _value;
   public TestClass() {
   }
   public TestClass(string value) {
    _value = value;
   }
   public string GetValue( string prefix ) {
   if( _value==null )
    return "NULL";
   else
     return prefix+" : "+_value;
   }
 
//获取类型信息
Type t = Type.GetType("TestSpace.TestClass");
//构造器的参数
object[] constuctParms = new object[]{"timmy"};
//根据类型创建对象
object dObj = Activator.CreateInstance(t,constuctParms);
//获取方法的信息
MethodInfo method = t.GetMethod("GetValue");
//调用方法的一些标志位，这里的含义是Public并且是实例方法，这也是默认的值
BindingFlags flag = BindingFlags.Public | BindingFlags.Instance;
//GetValue方法的参数
object[] parameters = new object[]{"Hello"};
//调用方法，用一个object接收返回值
object returnValue = method.Invoke(dObj,flag,Type.DefaultBinder,parameters,null);