FInd Process “unused memory size” with in “private bytes” using c#

As I understand Process "PrivateMemorySize64" (process.PrivateMemorySize64) contains unused memory allocated by CLR. Is there a way, I can program and find the amount of unused memory in private bytes using C#? I am selecting the process from another process and listing memory size. but since private byte also contains the "unused memory" allocated by clr, it is getting difficult for me to find the actual memory consumed by process.