How to Check a user is already logged on or not in c# winform

Dear you can manage in data base and services also

the logic of login and logout is very simple but to maintenance very difficult

first in login time update set value true and at the time of logout time set false  in data base


like

TableUser

UseId 1
UserCode EMp001
UserName SAROJ
Logon true



you can get all logon user using get select Query 

Select * From TableUser where Logon =true

make sure make one utility to realese to user becoze when if you directly close the application or restart the pc  so in data base we get wrong value so check at login time in your application user log on then using another utility you can set Logon value false