Question

Someone gave me this code that works great. But I would really like to understand what is happening inside it. Could somebody explain please? What is the meaning of each part of the code? The code is inside a custom control which has two labels inside a panel.

Also I’ve seen some custom control events that use add/remove syntax, what is that for? What is the difference with what is happening here?

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

See my comments below. Also for a more detailed event I blogged on this concept a while back where I go into more detail on the entire process.

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);
    }
}