Attribute

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ReflectionClass
{
    public enum Fruit
    {
        Apple,
        Banana,
        Pear,
        Watermelon
    }

    public class FruitTypeAttribute:System.Attribute
    {
        public FruitTypeAttribute(Fruit fruit)
        {
            this.fruit = fruit;
        }

        protected Fruit fruit;
        public Fruit TheFruit
        {
            get { return fruit; }
            set { fruit = value; }
        }
    }

    public class FruitTest:IFruit
    {
        [FruitType(Fruit.Apple)]
        public void AppleMethod() { }

        [FruitType(Fruit.Pear)]
        public void PearMethod() { }
    }
}

在使用Attribute的时候[FruitType(Fruit.Apple)]实际上就是实现了FruitTypeAttribute的构造方法，而在构造方法中又为TheFruit属性赋值。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;

namespace ReflectionTest
{
    class AssemblyTest
    {
        public static Assembly ReflectionClassAssembly
        {
            get
            {
                return Assembly.Load("ReflectionClass");
            }
        }

        public static void ShowAttributeInfo()
        {
            //object fruitTest = ReflectionClassAssembly.CreateInstance("ReflectionClass.FruitTest");
            Type fruitTest = ReflectionClassAssembly.GetType("ReflectionClass.FruitTest");
            MethodInfo method = fruitTest.GetMethod("AppleMethod", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);//可省略第二个参数
            
            Type fruitType = ReflectionClassAssembly.GetType("ReflectionClass.FruitTypeAttribute");
            Attribute attr = Attribute.GetCustomAttribute(method, fruitType);
            if (attr!=null)
            {
                PropertyInfo property = fruitType.GetProperty("TheFruit", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic);//可省略第二个参数
                Console.WriteLine("the {0} attribute is : {1}", method.Name, property.GetValue(attr, null));                
            }
            //Attribute[] attrs = Attribute.GetCustomAttributes(method);
            //if (attrs.Length > 0)
            //{
                //Console.WriteLine("the {0} attribute is : {1}",method.Name,property.GetValue(attrs[0],null));
                //((ReflectionClass.FruitTypeAttribute)attrs[0]).TheFruit
            //}
        }
    }
}