Hi logimatic,

Unfortunately there is no zoom to functionality or 'view all' capability when it comes to a series that takes up little space in the map.  If you are manually providing points to the polyline series then you should be able to calculate the min/max longitude and latitude from all those points and with the min/max you can update the maps WindowRect to encompass that rectangle.  GetZoomFromGeographic will help you construct that new window rect.

// calculate the min/max longitude and latitudes of your polyline points
var minLongitude = GetMinLongitude();
var maxLongitude = GetMaxLongitude();
var minLatitude = GetMinLatitude();
var maxLatitude = GetMaxLatitude();

// use the GetZoomFromGeographic method to generate a new WindowRect
var rect = this.geoMap.GetZoomFromGeographic(new Point(minLongitude, minLatitude), new Point(maxLongitude, maxLatitude));
this.geoMap.WindowRect = rect;