Working with DGN Files
A MicroStation document file is called a DGN file. A DGN file is composed of one or more models, each of which is represented using elements such as lines, arcs, and shapes. The File tab has items for creating, opening, and saving DGN files. Many of these file management operations and others can also be performed from the Work page or File Open dialog.
You can have only one DGN file open at a time. If you open a DGN file when one is already open, the first file automatically closes.
You can, however, view the models contained in other DGN files by attaching them as references to the active model in the open DGN file.
When you create a DGN file, MicroStation copies one of the provided templates or seed DGN files to the new file.