[quote user="Maury"]SolidPrimitive.CreateDgnExtrusion[/quote]
[quote user="Brien Bastings"]SolidPrimitive.CreateDgnBox [/quote]
Good answers to a different question: those methods from the MicroStationAPI are not echoed in the DgnPlatformNET API, which is what the questioner asked. I'm looking forward to finding a more complete DgnPlatformNET in a future MicroStation CONNECT.