WPF ContextMenu for Markers of LineSeries and ScatterSeries

Hi, Im trying to create a ContextMenu for markers of LineSeries and ScatterSeries.
Due there's no build in option, Im trying to get the current clicked (or nearest) clicked marker of multiple series inside the Plot.
I refered to the MouseEventExample, but I don't know how to transform the mouse position in WPF, because there are many methods that have been used in the example missing.
Any Ideas?

For more information here, refer to my question on StackOverflow:

http://stackoverflow.com/questions/33873750/oxyplot-contextmenu-for-markers-in-wpf