add_marker.cs

private void HMap_MapClick(object sender, HuaweiMap.MapClickEventArgs e)
{
   selectedCoordinates.LatLng = e.P0;
   if (circle != null)
   {
       circle.Remove();
       circle = null;
   }
   AddMarkerOnMap();
}

void AddMarkerOnMap()
{
    if (marker != null) marker.Remove();
    var markerOption = new MarkerOptions()
        .InvokeTitle("You are here now")
        .InvokePosition(selectedCoordinates.LatLng);

    hMap.SetInfoWindowAdapter(new MapInfoWindowAdapter(this));
    marker = hMap.AddMarker(markerOption);
    bool isInfoWindowShown = marker.IsInfoWindowShown;
    if (isInfoWindowShown)
        marker.HideInfoWindow();
    else
        marker.ShowInfoWindow();
}