windows phone 8 - Add fixed MapLayer once -

in application have map first thing (on launching) add custom maplayer (which populate many mapoverlays/pushpins).

when browse page of app , return map page, (ie maplayer drawn on map) gone.

it takes time add on again each time user navigates map page fixed, drawn/added once.

any suggestions?

edit, added code [i removed details, structure remains same]:

private async void drawstations()         {              sqliteasyncconnection conn = new sqliteasyncconnection("stasy.sqlite");              list<line1_stations> lines = await conn.queryasync<line1_stations>("select *...");              microsoft.phone.maps.controls.maplayer layer = new microsoft.phone.maps.controls.maplayer();              pushpin p;              foreach (line1_stations in lines)             {                 double slat = convert.todouble(a.lat);                 double slon = convert.todouble(a.lon);                  p = new pushpin();                 p.location = new geocoordinate(slat, slon);                 p.tap += img_tap;                 p.content = "...";                 p.foreground = new solidcolorbrush(colors.transparent);                 p.width = 30;                 p.height = 30;                  mapoverlay overlay1 = new mapoverlay();                 overlay1.content = p;                 overlay1.geocoordinate = new geocoordinate(slat, slon);                 overlay1.positionorigin = new point(0.0, 1.0);                 layer.add(overlay1);             }              mymap.layers.add(layer);         } 

you can try create maplayer public property in app.xaml.cs , set when app running first time.

then create instance of app inside page map , add maplayer map layers inside onnavigatedto event.