Thank you for writing.
Basically, all property changes fire the PropertyChanged event. However, this event is fired at the base element that has this property exposed. Depending on the structure of a RadControl, the properties that you can see exposed at this RadControl may only be shortcuts, but not the original properties. So you should not expect to get the PropertyChanged event fired at the control, but you should expect to get it fired at the element that has the original property exposed. We do not have a certain specification and a list describing which property is a core property at which element since these specifics highly vary on the different purposes (hence structures) of the controls.
In regards to the RadDropDownList control, generally you should be able to get the PropertyChange fired with SelectedValue arguments at the ListElement:
sender, PropertyChangedEventArgs e)
// do sth here
However, currently we have an issue which will prevent you from experiencing this behavior. We will address it in the upcoming major release Q3 2010.
I hope this information answers your questions.
the Telerik team
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