Called whenever the control's template changes.
Assembly: PresentationFramework (in PresentationFramework.dll)
The timing for changing the template is as follows:
The template is changed by a SetValue method call, a style trigger, or some other means.
The property value changes; the property-changed callback is called.
The old visual tree is removed.
An internal method is called which eventually calls the method.
Later, during a measure, OnApplyTemplate is called and a new visual tree is attached.
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2