c# - Store difference between two dates recursively and calculate time spent on web site -

i have find time spent on site choose maintain 2 datetimes , time in database can save difference between login time , logout time , store in table column timespent.

the time stored {00:16:58.413785200} have add amount of time recursively after each logout if spent 10 minutes in first login , 5 minutes in 2nd login have store 15 min timspent on site.

but problem not able guess happens if want add 2 minutes after 23:59:59.000000000. know max time value 23:59:59 can stored time datatype in sql.

so how achieve this? have tried

 var _user = db.users.singleordefault(t => t.id == id);  _user.endtime = datetime.now;  var _starttime = _user.starttime;  if (_user.timespent != null)  {    _user.timespent = _user.timespent + (_user.endtime - _starttime);  }  else  {    _user.timespent = (_user.endtime - _starttime);  }  db.savechanges(); 

you need switch datatype on timespent column bigint. should have default value of 0 timespent column aswell or handle in code.

var _user = db.users.singleordefault(t => t.id == id);  _user.endtime = datetime.now; var _starttime = _user.starttime;  timespan timespent = _user.timespent != null ? timespan.fromticks(_user.timespent) : 0; if (timespent > timespan.zero) {    timespent = timespent + (_user.endtime - _starttime) } else {   timespent = _user.endtime - _starttime }  _user.timespent = timespent.ticks;  db.savechanges();