触发事件的事件

Question

我有一个对象，它在我的类中是私有的。如果该对象触发了一个事件，我希望将该事件传递给正在使用我的类的任何对象。目前我是这样做的，我在我的构造函数中放入：

cbName.CheckedChanged += ((sender, args) => this.CheckChanged(this,args));

有没有更好的方法来做到这一点，有没有像类不会被释放这样的陷阱，因为它本身有一个事件，我需要在dispose函数中手动取消订阅？

将发送方从触发对象更改为this是可选的。

测试代码的完整版本

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace placeholder
{
    internal class FilterBase : UserControl, IFilterObject
    {
        public FilterBase(string name)
        {
            InitializeComponent();
            cbName.CheckedChanged += ((sender, args) => this.CheckChanged(this,args));
            cbName.Name = name;
            this.Name = name;
        }

        private CheckBox cbName;
        /// <summary> 
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary> 
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Component Designer generated code

        /// <summary> 
        /// Required method for Designer support - do not modify 
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            this.cbName = new System.Windows.Forms.CheckBox();
            this.SuspendLayout();
            // 
            // cbName
            // 
            this.cbName.AutoSize = true;
            this.cbName.Location = new System.Drawing.Point(4, 4);
            this.cbName.Name = "cbName";
            this.cbName.Size = new System.Drawing.Size(79, 17);
            this.cbName.TabIndex = 0;
            this.cbName.Text = "Filter Name";
            this.cbName.UseVisualStyleBackColor = true;
            // 
            // UserControl1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.AutoSize = true;
            this.AutoSizeMode = System.Windows.Forms.AutoSizeMode.GrowAndShrink;
            this.Controls.Add(this.cbName);
            this.Name = "Filter Name";
            this.Size = new System.Drawing.Size(86, 24);
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        public event EventHandler CheckChanged;
        public bool Checked
        {
            get { return cbName.Checked; }
        }
    }
}

Answer 1

event实际上类似于自动属性。您可以定义自己的add和remove方法，将委托直接传递给子控件，从而消除额外级别的间接性：

public event EventHandler CheckChanged {
    add { cbName.CheckChanged += value; }
    remove { cbName.CheckChanged -= value; }
}

这将删除存储在类中的额外Delegate (因为Delegate字段在标准事件的幕后使用)

Answer 2

嗯，这将防止当前对象在cbName活动时被垃圾回收，但听起来这不太可能是一个问题……这是固有的事实，无论您做什么(因为您想要触发该对象的CheckChanged处理程序)，都会获得对this的引用。

这样做的一个缺点是，即使你想取消订阅，也不能取消订阅(例如，在Dispose方法中)。另一种方法是使用实际的方法：

private void CbNameCheckedChangedHandler(object sender, EventArgs e)
{
    CheckedChanged(this, args);
}

...
cbName.CheckedChanged += CbNameCheckedChangedHandler;

// If you ever want to remove the handler
cbName.CheckedChanged -= CbNameCheckedChangedHandler;

请注意，这都是假设您的CheckedChanged事件是空安全的，例如，它被声明为：

public event EventHandler CheckedChanged = delegate {};

否则，如果没有人订阅该事件，当cbName.CheckedChanged触发时，您将获得一个NullReferenceException。