Returns the length of a single iteration of this Timeline.
Assembly: PresentationCore (in PresentationCore.dll)
This method should only be called when the Duration property is set to Automatic. If Duration is Automatic, the natural duration is determined by that particular class's implementation of GetNaturalDurationCore.
Note that passing this method a clock other than the one that was created for this timeline is possible, but will provide unreliable results.