Compiled Fortran dll doesn't run on the available cores when invoked by a .net app

Hi,
I've compiled a fortran code as a DLL using the auto-parallization and auto-vectorization features in fortran compiler.
When I call the dll using a fortran compiled exe program, the dll runs faster on all the available cores on my PC.
However, when I call the DLL using a .net compiled exe, the dll runs slower and only on just one core.

Can I get help on this topic?

Thanks,