c# - 解释用户控件中自定义事件的代码

Question

有人给了我这段代码，效果很好。但我真的很想了解里面发生了什么。有人可以解释一下吗？代码各部分的含义是什么？该代码位于自定义控件内，该控件在面板内有两个标签。

我还看到了一些使用添加/删除语法的自定义控件事件，那是干什么用的？与这里发生的事情有什么区别？

public partial class UserControl1 : UserControl
{
    public UserControl1()
    {
        InitializeComponent();
    }

    public event EventHandler MyCustomClickEvent;

    protected virtual void OnMyCustomClickEvent(EventArgs e)
    {
        // Here, you use the "this" so it's your own control. You can also
        // customize the EventArgs to pass something you'd like.

        if (MyCustomClickEvent != null)
            MyCustomClickEvent(this, e);
    }

    private void label1_Click(object sender, EventArgs e)
    {
        OnMyCustomClickEvent(EventArgs.Empty);
    }
}

Answer 1

请参阅下面我的评论。同样对于更详细的事件我blogged前段时间我在这个概念上详细介绍了整个过程。

public partial class UserControl1 : UserControl
{
    //This is the standard constructor of a user control
    public UserControl1()
    {
        InitializeComponent();
    }

    //This defines an event called "MyCustomClickEvent", which is a generic
    //event handler.  (EventHander is a delegate definition that defines the contract
    //of what information will be shared by the event.  In this case a single parameter
    //of an EventArgs object.
    public event EventHandler MyCustomClickEvent;


    //This method is used to raise the event, when the event should be raised, 
    //this method will check to see if there are any subscribers, if there are, 
    //it raises the event
    protected virtual void OnMyCustomClickEvent(EventArgs e)
    {
        // Here, you use the "this" so it's your own control. You can also
        // customize the EventArgs to pass something you'd like.

        if (MyCustomClickEvent != null)
            MyCustomClickEvent(this, e);
    }

    private void label1_Click(object sender, EventArgs e)
    {
        OnMyCustomClickEvent(EventArgs.Empty);
    }
}