How to bubble an event up multiple levels?

Question

I'm struggling to bubble an event correctly.

I have a master page with a user control, and a page that is a child of the master page.

The user control and the page share common data, so when the user control updates, it updates the apage and vice versa.

The user control exposed an event to the master page. This is the format I use.

outside of class:

public delegate void OfferBookmarkRemoved(int OfferID);

inside class:

public event OfferBookmarkRemoved OfferBookmarkRemoved;

protected void LV_Bookmarks_ItemCommand(object source, ListViewCommandEventArgs e)
{
    if (e.CommandName == "RemoveOffer")
    {
        var offerId = (int)e.CommandArgument;

        OnOfferBookmarkRemoved(offerId);
    }

}

void OnOfferBookmarkRemoved(int offerId)
{
    offerId.ThrowDefault("offerId");

    if (OfferBookmarkRemoved != null)
    {
        OfferBookmarkRemoved(offerId);
    }
}

Now this can be used in the master page ok. I don't do anything in the master page and want to expose the event so that the aspx page can use it, like this:

Master.OfferBookmarkRemoved += OnBookmarkRemoved;

void OnBookmarkRemoved(int offerId)
{
    offerId.ThrowDefault("offerId");

    OfferList1.UpdateBookmark(offerId);
}

So the missing bit is to listen for the event in the master and make it available to the page.

Can anyone help?

Answer 1

You need to define this event in the master page also like that:

public event EventHandler<OfferEventArgs> OfferBookmarkRemoved
{
   add
   {
       userControl.OfferBookmarkRemoved += value;
   }
   remove
   {
       userControl.OfferBookmarkRemoved -= value;
   }
}

This way any page that registers to the master event will be registered to the usercontrol event.

By the way, you are not following the event pattern. Your event should look like:

public class OfferEventArgs : EventArgs
{
   public int OfferID { get; set; }
}

public event EventHandler<OfferEventArgs> OfferBookmarkRemoved;

and when invoked:

OfferBookmarkRemoved(new OfferEventArgs() { OfferID = offerId });