Preventing Multiple Login- Comparing Current Session ID with new Session ID

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C#

ASP.NET

SQL

I have created a Login function where every user shall Login with a new Session ID that will prevent other users (B), not to login till the current user (A) logout. Now my problem is that if any other user (B) got his hand on the Link of the of the current user (A). The other user (B) will directly go to the current user (A)'s account without any authentication. And I think I have a solution, yet I lack in syntax as well :$ What I want is to store that current user (A) session ID in the database and I will create a seperate colomn for it in my userLogin table. If I just store the current user (A) Session ID in that colomn where it will prevent the other user (B) not to grab his access even if he got his hands on the Session ID then will it work? if Yes, then How? (Please type all the neccesary Code) and if No, the How can I..?