public double?GetDistanceTo(User user) { var l1 = GetLocation(); var l2 = user.GetLocation(); if (l1 == null || l2 == null || l1.Latitude == null || l1.Longitude == null || l2.Latitude == null || l2.Longitude == null) { return(null); } var sCoord = new GeoCoordinate((double)l1.Latitude, (double)l1.Longitude); var eCoord = new GeoCoordinate((double)l2.Latitude, (double)l2.Longitude); return(sCoord.GetDistanceTo(eCoord) / 1000); }