oxyplot/oxyplot — pull request #260 by GeertvanHorrik (2014-11-25 14:56:56+00:00)
Title: #259 Improved rendering performance for WPF by only rendering the plots ...

...that are actually really visible to the user (this ensures major improvements in large lists)

Note 1) I hope I followed your coding convention. It is quite different than other projects I am used to, but hopefully it's to your satisfaction.
Note 2) I added an example (PerformanceDemo) for WPF (4.0 and 4.5). It shows you a large list of plots that will render slower (and these are very simple plots without external annotations, etc) without the new feature.

I have tested this against my app, and before it was un-runnable, now it works great!