Repair Corrupt DGN with EDG in Microstation

Follow these steps in order:

1. Create a good file using the same settings as the file that has gone bad. The preferred method is to copy the original seed file to a new file named GOOD.DGN.
2. It is recommended that you copy both the bad and good files into the EdG directory (the default is \win32app\ustation\EdG or \Bentley\program\EdG). This will save the trouble of entering path statements.
3. Backup the bad design file. There is no undo function in EdG.
4. Change to the EdG directory.
5. At the command prompt, enter the following commands:

edg good.dgn (Enter the EdG environment with the good file)
open new.dgn (Create a new output within EdG)
edg bad.dgn (Open the damaged file; substitute the name of your corrupted file)
patch wtf (Enter the patch facility of EdG)
0 (Zero sets the Words-to-Follow value to zero)
a 5 (Instruct EdG to search and not stop until 5 valid elements are found)
save (Exit the patch facility and save the patched element)
type next (Move one element further into the design)
write rest (Write all elements into NEW.DGN)
close (Close NEW.DGN)
exit (Exit EdG)

The file NEW.DGN will be your new, good file.

I did it like this:
C:\>cd C:\Bentley\Program\EDG

File is repaired!