What is the way to maintain data specific to users in ASP.NET application when different user logged in from different machines

 After login to MVC application initializing data using below statements and All are static variables. Data coming from DB if the login is successful.
iRISConstants.UserID = row["UserID"].ToString();
iRISConstants.SessionID = row["SessionID"].ToString();

Maintaining this data in static variables since after user login if he do any transaction i have to pass UserID and SessionID to SP call
Here is the problem when hosted the application on IIS server.
1. User login from one machine and variable are initialized.
2. Another user log in to machine and variable get override.
The user id is updated and whatever the transaction do from both first user or second user sending second userID and sessionID since the static data assigned with second logged in user details.
What is the way to resolve it

What I have tried:

<pre>i tried sessions.
1.When one user login i store first user in session variable 
2.When other user log in store second user in different session varible
Lets say both(Different) user logged in some user did transaction i want to send that particular user UserID and SessionID to SP call 
Is there any way to know which user is doing transaction because we are getting only user information during user login, later i have maintain it from application as SP required those 2 parameter