windows phone 8.1 - Getting the position of the point where the user taps on a map -

windows phone 8.1 - Getting the position of the point where the user taps on a map -

how can latitude , longitude of point user taps on map?

i tried doing this:

class="lang-cs prettyprint-override">geocoordinate position = mymap.convertviewportpointtogeocoordinate( e.getposition(mymap));

but error there's no definition convertviewportpointtogeocoordinate.

maps windows-phone-8.1