WP - How to constantly update my location - mvvm

Question

Currently my location not updating when I change it to different location via emulator. But it will change after I restart my application. This is what I write when the app launch
private void Application_Launching(object sender, LaunchingEventArgs e)
{
IsolatedStorageSettings Settings = IsolatedStorageSettings.ApplicationSettings;
GeoCoordinate DefaultLocation = new GeoCoordinate(-6.595139, 106.793801);
Library.GPSServices MyGPS;
if (!Settings.Contains("FirstLaunch") || (bool)Settings["FirstLaunch"] == true)
{
Settings["FirstLaunch"] = false;
Settings["LastLocation"] = DefaultLocation;
Settings["SearchRadius"] = 1;
}
//If key not exist OR key value was set to false, ask for permission to use location
if (!Settings.Contains("LocationService") || (bool)Settings["LocationService"] == false)
{
var result = MessageBox.Show(
"Jendela Bogor need to know your location to work correctly, do you want to allow it?",
"Allow access to your location?",
MessageBoxButton.OKCancel);
if (result == MessageBoxResult.OK)
{
Settings["LocationService"] = true;
MyGPS = new Library.GPSServices();
}
else
{
Settings["LocationService"] = false;
}
Settings.Save();
}
else if ((bool)Settings["LocationService"] == true)
{
MyGPS = new Library.GPSServices();
}
}
I store my location in my application setting IsolatedStorage with name Settings["LastLocation"]
How should I do to constantly update my location in the Background using MVVM Pattern (MVVM-Light) so my PushPin on map in the ThirdPageView always updated?
EDIT
public GPSServices()
{
if ((bool)Settings["LocationService"] == true)
{
if (_watcher == null)
{
_watcher = new GeoCoordinateWatcher(GeoPositionAccuracy.High);
_watcher.MovementThreshold = 20;
}
StartWatcher();
_watcher.PositionChanged += new EventHandler<GeoPositionChangedEventArgs<GeoCoordinate>>(watcher_PositionChanged);
_watcher.StatusChanged += new EventHandler<GeoPositionStatusChangedEventArgs>(watcher_StatusChanged);
}
else if ((bool)Settings["LocationService"] == false)
{
StopWatcher();
}
}
private void StartWatcher()
{
_watcher.Start();
}
private void StopWatcher()
{
if (_watcher != null)
_watcher.Stop();
}
private void watcher_PositionChanged(object sender, GeoPositionChangedEventArgs<GeoCoordinate> e)
{
if (e.Position.Location.IsUnknown)
{
MessageBox.Show("Please wait while your position is determined....");
return;
}
Settings["LastLocation"] = e.Position.Location;
Settings.Save();
}

Answer 1

System.Device.Location.GeoCoordinateWatcher provides what you need.
var geoWatcher = new GeoCoordinateWatcher(GeoPositionAccuracy.High);
// This event fires every time the device location changes
geoWatcher.PositionChanged += (s, e) => {
//e.Position.Location will contain the current GeoCoordinate
};
geoWatcher.TryStart(false, TimeSpan.FromMilliseconds(2000));

Answer 2

is this helpful for you ? using GeocoordinateWatcher.PositionChanged event?
public Location()
{
GeoCoordinateWatcher location == new GeoCoordinateWatcher();
location.PositionChanged += new EventHandler<GeoPositionChangedEventArgs<GeoCoordinate>>(location_PositionChanged);
location.Start();
}
//event to track the location change
public void location_PositionChanged(object sender, GeoPositionChangedEventArgs<GeoCoordinate> e)
{
}