One of my colleges replied your question in the Hide Vertical Scrollbar
forum. The next following lines are quoted from there:
"Unfortunately, there is no built-in functionality for getting the number of the visualized points. However, you can count those UIElements manually.
In order to do this you can use the GetDataPointVisual() method of the series. You can traverse all data points of the series and call that method for everyone."
Check out Telerik Analytics, the service which allows developers to discover app usage patterns, analyze user data, log exceptions, solve problems and profile application performance at run time. Watch the videos
and start improving your app based on facts, not hunches.