GMap .net offline

you can create a separate program to prefetch tiles for offline use. Or use the GMap NET demo program (https://github.com/radioman/greatmaps/tree/master/Demo.WindowsPresentation)

The code below is for a button press after you've selected an area using ALT + mouse first button.

        RectLatLng area = mapView.SelectedArea;

        if (!area.IsEmpty)
        {
            for (int i = (int)mapView.Zoom; i <= mapView.MaxZoom; i++)
            {
                TilePrefetcher obj = new TilePrefetcher();
                obj.Title = "Prefetching Tiles";
                obj.Icon = this.Icon;
                obj.Owner = this;
                obj.ShowCompleteMessage = false;
                obj.Start(area, i, mapView.MapProvider, 100);
            }

            DialogResult = true;
            Close();
        }
        else
        {
            MessageBox.Show("No Area Chosen", "Error", MessageBoxButton.OK, MessageBoxImage.Error);
        }

(mostly copied from Gmap NET Demo source)

https://github.com/radioman/greatmaps/tree/master/Demo.WindowsPresentation

The Files are stored in C:\Users\[your user name]\AppData\Local\GMap.NET\TileDBv5\en

Once you've successfully prefetched the tiles you can copy the files to the same location in the offline pc and it should use it (or just copy the whole GMap.NET folder to the offline pc via usb or whatever)