zCane75:
Is one of the references above including that?
Yes, it is bentley.interop.microstationdgn
zCane75:
Probably now I understand what confuses you.
MVBA hides usage of Application class and usage of MicroStationDGN namespace, so you can use its functions directly. In .NET there is no any default object, so you must explicitly use a MicroStationDGN.Application interface instace.
To obtain an instance of MicroStationDGN.Application interface you need assembly bentley.microstation. There is a class Bentley.MicroStation.InteropServices.Utilities, which has a property ComApp.
Use it as follows:
using BIM = Bentley.Interop.MicroStationDGN;
...
BIM.Application ustn = Bentley.MicroStation.InteropServices.Utilities.ComApp;
BIM.Element floodBoundary = ustn.GetFloodBoundary(...);
HTH