View page anonymously, but require password to use page functions

Hi,
My site is designed with VS2017 using asp.net and vb.net.

I would like for any visitor to be able to view my site anonymously, but if they want to post a message on my site or use other functions then they need to register and get a username and password.

VS has login controls that allow users to register before they can view a page, but that's too radical. I would like viewers to see a page and then register if they want to access the functions on the page.

Any suggestions?

Thanks!