public void Update(DateTime dt, double tm)
{
var timeTable = TimeTables.Where(t => t.Date == dt).FirstOrDefault();
if (timeTable == null)
{
timeTable = new TimeTable();
timeTable.Date = dt;
//throw new ArgumentNullException("timeTable");
}
timeTable.PlanningTime = tm;
ChangeTracker.DetectChanges();
TimeTables.AddOrUpdate(timeTable);
SaveChanges();
}
