So I recently needed to connect into an ArcSDE database (direct connect) using the Operating System login and I realized that I had no idea how to do it.

Luckily, ESRI have a great EDN post about it which explains everything.

Essentially, you do not populate the IPropertySet with the USER and PASSWORD values but rather set the AUTHENTICATION_MODE to OSA.

The rest of the connection parameters are the same and since we normally use connection files in our applications it means that the connection file just needs to be changed.

GEOPRESS_LOCATION(Home)