Classes
In MicroStation DGN files, element display can be controlled based on the element´'s class. Construction class is commonly used for geometry that is useful for construction purposes, but is not considered part of the actual model. MicroStation uses the Pattern class for all area and linear pattern geometry. When linear patterning is applied to an element, the element class is changed to linear patterned. As it is not desirable to display both an element and its linear pattern geometry, turning on a view Pattern display attribute automatically disables display of linear patterned geometry.
DWG files do not have analogous concepts. Associated patterns are saved as hatch entities and can be controlled (along with filled geometry) with the AutoCAD FILLMODE setting, but non-associative and linear patterns are saved as simple geometry and therefore have no such control.
Working with Classes That Will Be Saved to DWG Files
If you are working with a DGN file that contains Construction, Pattern, or Linear Patterned class elements, you can define how these classes will be saved to the DWG file. To do this, use the Classes options on the Save As DWG/DXF Options dialog.