.NET Framework 4.6 and 4.5
Protected Overridable Sub OnClosing ( _
e As CancelEventArgs _
OnClosing raises the Closing event.
A type that derives from Window may override OnClosing. The overridden method must call OnClosing on the base class if Closing needs to be raised.
Supported in: 4.6, 4.5, 4, 3.5, 3.0
.NET Framework Client Profile
Supported in: 4, 3.5 SP1