How to call dismapi.dll on Windows 7

How do I install the DISMAPI on Windows 7?

There is the function DismGetDrivers that I want to use on Windows 7. According to the documentation it is supported on Windows 7. However a program I have written that calls the dismapi.dll reports:

Unhandled Exception: System.DllNotFoundException: Unable to load DLL 'DismApi':
The specified module could not be found. (Exception from HRESULT: 0x8007007E).

The program works as expected on Windows 8.1.

I am thinking there is probably some toolkit that needs to be installed. I thought installing the Windows 7 ADK would help but it has made no difference. I also installed the MDT. No improvement.