Bentley Map is delivered with a small sample of prepared cartographic linestyles: Highway, Path, Divided Highway, Railroad, River, Local and Arterial. These styles are available with the geo_example workspace. For all other workspaces, the Cartographic Style Manager will appear as follows:
To use the delivered styles, simply copy
...\Projects\Examples\Geospatial\geo_example\designer\dgnlib\linestyles.dgnlib
to your workspace dgnlib folder.
Of course the configuration variable MS_DGNLIBLIST will need to be pointing to this folder in order to populate the Cartographic Style Manager.