When does WPF subscribe to the PropertyChanged event?

Question

I have a ClassA with an ObservableCollection property, that implements the INotifyPropertyChanged interface

on my window codebehind I have declared a ClassA variable, and initialize it in the Main() method.

i'd expect that variable.PropertyChanged would have a WPF event wired to it, but apparently the PropertyChanged event remains null

score 12 · Accepted Answer · answered Aug 26 '09 at 19:31

12

WPF will subscribe to the PropertyChanged event when you bind to your object. This is the core way that databinding works.

It actually does this via the PropertyChangedEventManager using the WeakEvent pattern in WPF.

answered Aug 26 '09 at 19:31

Reed Copsey

So... WPF will also unsubscribe when the binding is discarded (therefore avoiding memory leaks)? – Néstor Sánchez A. Mar 20 '12 at 18:46
1

@NéstorSánchezA. It uses the weak event pattern to avoid the memory leak. In general, you shouldn't have a leak problem due to WPF binding. – Reed Copsey Mar 20 '12 at 19:03

score 0 · Answer 2 · answered Aug 27 '09 at 02:57

0

I'm not sure if this exactly answers your question, but I had similar experiences, and blogged about it here.

Essentially, make sure the DataContext is not null when the binding occurs, such that PropertyChanged events can get back to the UI...

answered Aug 27 '09 at 02:57

kiwipom

2 Answers2