This reproduces the issue described in this WPF bug report.
See the comments in Styles\Styles.xaml for details about how this project reproduces the conditions that cause this WPF performance bottleneck.
When running the application, the right hand side of the view contains elements that control and diagnose the problem. The left hand side contains the elements that cause deferred resource references to be accumulated.
The Count: field uses reflection to display the total number of elements in the internal
_deferredResourceReferences field of every resource dictionary merged into the application’s resources.