如何判断事件已经被注册过?

Question

如以下语句,我注册后 但可能在一个方法中会被重复调用.如果重复注册没必要.如何判断此事件已经被注册过了呢？或有其它的办法？谢谢
ExperimentManager.Instance.refreshUI += new ExperimentManager.RefreshUI(Instance_refreshUI);

Answer 1

写成这样问题不就解决了ExperimentManager.Instance.refreshUI -= new ExperimentManager.RefreshUI(Instance_refreshUI);
ExperimentManager.Instance.refreshUI += new ExperimentManager.RefreshUI(Instance_refreshUI);

Answer 2

ExperimentManager.Instance.refreshUI -= new ExperimentManager.RefreshUI(Instance_refreshUI);
ExperimentManager.Instance.refreshUI += new ExperimentManager.RefreshUI(Instance_refreshUI);注册之前先-=下

Answer 3

可以通过反射获得，比如如下代码可以判断一个Form是否绑定过Load事件，已经绑定的方法名是什么
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.Reflection;
namespace WindowsApplication19
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();            this.Load+=new EventHandler(Form1_Load1);
            this.Load+=new EventHandler(Form1_Load2);            PropertyInfo propertyInfo = (typeof(Form)).GetProperty("Events", BindingFlags.Instance | BindingFlags.NonPublic);
            EventHandlerList eventHandlerList = (EventHandlerList)propertyInfo.GetValue(this, null);
            FieldInfo fieldInfo = (typeof(Form)).GetField("EVENT_LOAD", BindingFlags.Static | BindingFlags.NonPublic);            Delegate d = eventHandlerList[fieldInfo.GetValue(null)];            if (d != null)
            {
                foreach (Delegate de in d.GetInvocationList())
                    Console.WriteLine(de.Method.Name);
            }
        }
        private void Form1_Load1(object sender, EventArgs e)
        {
            //什么也不干
        }
        private void Form1_Load2(object sender, EventArgs e)
        {
            //什么也不干
        }
    }
}

Answer 4

放一个list或者hashtable，没添加一次事件就记录个名称，下次注册时先判断是否有这个名称

Answer 5

1、先移动再注册(-= +=)
2、定义一个泛型 类型 add 之前先判断