3 Answers, 1 is accepted
I tried to reproduce the described behavior but was unable to. The Close event is fired which is expected.
I've made a sample project in which the Close event fires a MessageBox whenever a pane is closed, regardless of the way it's closed. Please review the project and let me know if it deliveres the desired result. If not, please update it with your logic, so I can investigate further.
The pane won't close on middle mouse button, except if the CloseTabsOnMouseMiddleButtonDown property of the RadPaneGroup is used. If this is the case, it's an expected behavior, since this property doesn't close the pane but removes it from the visual tree, hence the Close event won't be raised.
Please, let me know if that answers your query.