how to remove user online from database after session end asp?

Do you REALLY want to remove the user from the database? You have to ask a more precise question. What I think you really want to do is remove the user's logon status from the database. For that, you would need to do something like this:

0) Add a DateTime column to the user logon status table.

1) Every time the user does something on the web site, update that column with the current date time.

2) Create a job in sql server based on a time interval (maybe 30 minutes) that scans that column for a last-update time that exceeds 30 minutes. If it finds one, remove that user's logon status from the table.

3) (Optional) Before the user is allowed to do anything, the code checks the logon status to see if they are still considers to be logged on. If so, they are allowed to proceed. If not, it asks them for credentials again.

4) You can also put code into the web site that contributes to the system.