I have a web application with admin area for managing content but the rest of the site is currently secured by ASP Identity that authenticates my public users. Now I need to authenticate some internal users to access the admin area.
Is this possible?
What you are looking for is known as SSO (Single Sign On). With SSO a user can login once and access multiple applications. There are great articles on the web about the implementation. Have a look at http://arunendapally.com/post/implementation-of-single-sign-on-(sso)-in-asp.net-mvc for a sample.