.Net Core Docker Unable to load DLL 'activeds.dll'

I have an ASP.Net Core application that runs fine on IISExpress.

I am completely new to Docker, so when I add Docker support to the project and run it chokes on this section:

DirectoryEntry processEntry = new DirectoryEntry("LDAP://MyLdap", user, password);
processEntry.Options.Referral = ReferralChasingOption.Subordinate;
DirectorySearcher searcher = new DirectorySearcher(processEntry);

With the error:

DllNotFoundException: Unable to load DLL 'activeds.dll' or one of its dependencies: The specified module could not be found. (Exception from HRESULT: 0x8007007E)

I figure this is because Docker can't see the dll so I added the following to the Dockerfile:

COPY ["C:/Windows/System32/activeds.dll","activeds.dll"]

But this did not seem to improve things, How do I make the dll available to the Docker Container?