Why am I getting the error “Cannot instantiate implementation type” for my generic service?

Question

I have a generic repository that I have been instantiating right in my WEB API Controller no problem for a while.

This is what my controller used to look like:

Answer 1

This happened to me recently. I had the implementation class marked "abstract", an artifact of an earlier design. I removed it and the container was able to instantiate the class without a problem.