Make sure COM+ is used from .NET

Hi,

How do we make sure that COM+ services are used when calling a COM object
from .NET ? I could have just register the DLL using regsvr32 and the call
would still work. My problem is that the legacy object I'm using needs to
read the infamous "constructor string" that is specified when doing the
setup in the component properties, and from the behavior I see, the
constructor string seems to not be passed...