tragets对使用属性事件用法 [英] Usage of tragets on events using attributes

问题描述

在事件（字段定义的事件）上使用属性时，有三种可能的属性目标，即事件，字段和方法。我理解事件和字段目标的使用，但方法目标适用于哪里。

There are three possible attribute targets when using attributes on events (field defined events) and those are event, field and method. i understand the usage of event and field target, but where does the method target apply.

例如

[AttributeUsage(AttributeTargets.All,AllowMultiple=false,Inherited=true)]
internal class TestAttribute : Attribute
{
}
internal class Test
{
    [event: Test]
    [field: Test]
    [method: Test]
    public event Action action;
}

推荐答案

，它适用于编译器生成的添加和删除方法（执行订阅/取消订阅的方法）：

As far as I can tell, it's applied to the "add" and "remove" methods generated by the compiler (the methods which perform the subscription/unsubscription):

using System;
using System.Reflection;
using System.Runtime.CompilerServices;

[AttributeUsage(AttributeTargets.All,AllowMultiple=false,Inherited=true)]
internal class TestAttribute : Attribute
{
}
internal class Test
{
    [event: Test]
    [field: Test]
    [method: Test]
    public event Action action;

    static void Main() 
    {
        MethodInfo method = typeof(Test).GetEvent("action")
                                        .GetRemoveMethod(); // Or GetAddMethod
        Console.WriteLine(method.IsDefined(typeof(TestAttribute), true));
    }
}

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