I have a third party dll (C++) which I need to call from my c# class. I
defined

[DllImport("The.dll")]
public static extern ...

for each function that I want to use. The brief API document for the
functions states that the return values from these functions can be H_FAIL
and H_SUCCESS. There also some structs that are used as parameters which in
turn can have values in the same form, e.g. H_NOT_INSTALLED.

There is no documentation so I can't figure out the actual values behind the
H_FAIL etc. I don't have any .h files, just the dll. Is there any way to
obtain these underlying values (I'm pretty sure they are all integers) using
the Interop? Or make my c# understand the H_SOMETHING?

Thanks in advance.

Anna