gmap.net - How to add multiple makers on Gmap in c# -

i have text file list of gps coordinates. trying place marker on each of coordinates document. problem lengths of documents change , way have it, marker gets replaced every iteration. how add marker each lat/lon point?

here's relevant code:

    private gmapoverlay gmapoverlay;     private gmapmarker marker;         gmap.mapprovider = gmap.net.mapproviders.googlemapprovider.instance;         gmap.minzoom = 2;         gmap.maxzoom = 25;         gmap.zoom = 5;         gmap.showcenter = false;         gmap.dragbutton = mousebuttons.left;          //setup map overlay displaying routes/points         gmapoverlay = new gmapoverlay("path");         gmap.overlays.add(gmapoverlay);         gmapoverlay.markers.clear();         gmapoverlay.routes.clear();          //gmarkergoogle marker = new gmarkergoogle(new pointlatlng(0, 0), gmarkergoogletype.green);         marker = new gmarkergoogle(new pointlatlng(0, 0), gmarkergoogletype.green);         marker.isvisible = false;         marker.tooltipmode = markertooltipmode.onmouseover;         marker.tooltiptext = "starting point";         gmapoverlay.markers.add(marker);      private void btn_kmlfile_click(object sender, eventargs e)     {         dialogresult result = openfiledialog4.showdialog();         if (result == dialogresult.ok)         {             string filename = openfiledialog4.filename;             string[] lines = system.io.file.readalllines(filename);             foreach (string line in lines)             {                 string[] data_array = line.split(',');                 double londecimal = convert.todouble(data_array[0]);                 double latdecimal = convert.todouble(data_array[1]);                 marker.position = new pointlatlng(latdecimal, londecimal);                 marker.isvisible = true;                 gmap.update();               }         }     }      private void openfiledialog4_fileok(object sender, canceleventargs e)     {         openfiledialog openfiledialog4 = new openfiledialog();     } 

the markers can go markers collection:

public readonly observablecollection<gmapmarker> markers; 

just add markers collection single marker.

edit

i assuming wpf client, there's no observable collection if using winforms. have tried add new marker collection original marker? in loop:

string[] data_array = line.split(','); double londecimal = convert.todouble(data_array[0]); double latdecimal = convert.todouble(data_array[1]); // add new 1 here var marker = new gmarkergoogle(new pointlatlng(latdecimal, londecimal), gmarkergoogletype.green); marker.isvisible = true; gmapoverlay.markers.add(marker);