Asp.net Session Variable from SQL DB

Question

I have built a Login Page where users saved to my UserDetail table can login to my web app. I am able to create a session variable from the username(email in this case) but i would like to pull UserId as the session variable instead.  

 

I am developing my Web App in visual studio c# Web Forms with a Sql Server Database.

 

Any Advice/Help is appreciated Thanks.

 

This is My Code for storing the session variable on the Login Page: