geocoding - C# GeoCoordinate Return Value -

i'm using function below find distance between 2 sets of latitude , longitude pairs. seems work fine have 2 questions. returns value in kilometers rather miles (i in us), , kilometer value seems off 3 decimal places? values returns this: 34366.7661043296 distance valencia, ca burbank, ca 35 kilometers. why in kilometers, , more importantly why decimal issue? great if returned 36.50 miles. appreciated, thank in advance.

        public static double getdistance(double slatitude, double slongitude, double elatitude, double elongitude)     {         var scoord = new geocoordinate(slatitude, slongitude);         var ecoord = new geocoordinate(elatitude, elongitude);         return scoord.getdistanceto(ecoord);                 }