How to identify a user to get unique views in .NET core?

I want to store unique user views on my videos. The concept is that if a user sees the video send a request to the backend. I thought that I will use user IP addresses in the backend and store it with the videoId like composite keys so these pairs will be unique. To get the IP address I find this on the Microsoft docs:

request.HttpContext.Connection.RemoteIpAddress;

I read in the documentation it can be null. Is it a good idea to use it. My other idea to use Session for it. How can I identify a user to get a broadly real view count on a video?

On the client-side, I Use reactJS.