Build your offline maps for Windows Phone 8.1 with MBTiles.

var uri = new Uri("ms-appx:https:///Maps/geography-class.mbtiles");
var file = await StorageFile.GetFileFromApplicationUriAsync(uri);
MapControl.TileSources.Add(MBTileSource.Create(file.Path));

See GeographyClass sample project for more details.

MBTiles are SQLite databases. Therefore, SQLitePCL package must be installed in a target project.

• SQLitePCL Installation Instructions
• MBTiles Specification