I am in a situaion where I have a set of idl files that I am building a
.NET assembly with.
using midl and tlbimp.

The problem that I have is that some of the interfaces return S_FALSE
which I need to detect in my C# program.

I can't modify the the idls and I don't want to do the ildasm/ilasm
thing because if the library changes and needs to be rebuilt there is
an intermediate step where I can lose work.

What I really want id MIDL to put the preservesig on everything. I am
okay with checking the HRESULTS on the C# side. Is there such a thing?

Or maybe I am going about this the wrong way,

any help appreciated