null value kills the binding

A short one this time: I am working on a silverlight project. Actually it spent several hours to find a simple truth:

If a property that is involved in a binding retruns null, the binding is dead.

That means that if the propery value changes later on and you raise a PropertyChanged event, your view will not get updated, because for any reason the binding engine does not call the properties getter any more.

Perhaps that saves some of you some valuable lifetime.