Responding to a WPF Click Event in a Data-bound User Control...

Question

I hope this makes sense.

I have created several WPF User Controls. The lowest level item is 'PostItNote.xaml'. Next, I have a 'NotesGroup.xaml' file that has an ItemsControl bound to a List of PostItNotes. Above that, I have a 'ProgrammerControl.xaml' file. Each ProgrammerControl has a grid with four different NotesGroup user controls on it (and each NotesGroup contains 0-many PostItNotes.

Then, I have my main window. It also has an ItemsControl, bound to a list of Programmers.

So, you end up with a high level visual view of a list of programmers, each programmer has four groups of tickets, each group of tickets has many PostItNotes.

The trouble I'm having, is that I want to respond to a mouse click event in my mainWindow's code behind file.

I can add a MouseClick event into my PostItNote.xaml.vb file and that is getting called when the user clicks a PostItNote, and I can re-raise the event; but I can't seem to get the NotesGroup to listen for that event. I'm not sure if that's even the correct approach.

When the user clicks the PostItNote, I'm going to do a bunch of business-logic type stuff that the PostItNote control doesn't have a reference to/doesn't know about it.

Can anyone point me in the right direction?

Answer 1

You have a couple choices:

1. Use the PreviewXXX events which are fired during the "tunneling" phase of WPF event routing. The parent controls can always preview the events going down through them to children.
2. Use the more advanced approach to hooking up events leveraging the AddHandler method to which you can pass a parameter called "handledEventsToo" which basically means you want to know when the event happened "within" you even if some descendent element handled the event itself.

Answer 2

I am going to take a flyer here. You probably don't want to be handling the event that high up; not really anyway. You are catching the event at the lower levels, which is unavoidable. Consider invoking a routed command from the PostItNote click event handler.

The routed commands bubble up and tunnel down through the tree. You can have an architecture where a high-level handler can listen to a logical event (Opening a postit note perhaps?). The handler for this doesn't need to care where the command originates from. It might be from you clicking something, it might be from clicking on a toolbar button. Both are valid scenarios.

It sounds like you are creating some kind of custom UI, am I right? You want the application to respond to the users interactions. That is what the RoutedCommands are for.