getting an int to decrement after an action - asp.net

Question

so in my person table...I have Id, Name & HolidaysRemaining.
Its for a holiday booking application, and atm when a user selects dates from a calendar and clicks the button, each date selected will be stored in the DB, I am trying to minus the holidays remaining by 1, as each holiday is booked, but it doesn't seem to be picking up.
//listHolidays in correct format dd/mm/yy
[HttpPost]
public ActionResult listHolidays(Holiday holiday, Person person , int? PersonId, string HolidayDate, string endDate, string AlreadyExists)
{
db.People.Attach(person);
//int holidaysRemaining = 20;
//person.HolidaysRemaining = holidaysRemaining;
DateTime startDates = Convert.ToDateTime(HolidayDate);
DateTime endDates = Convert.ToDateTime(endDate);
try{
while (startDates <= endDates)
{
if (startDates.DayOfWeek != DayOfWeek.Saturday && startDates.DayOfWeek != DayOfWeek.Sunday)
{
//if user selects Holiday that already exists, wont add it to Db
//gets string, and uses the previously converted to dateTime 'startDate'
//id so only applies to person creating holidays
ViewBag.CantDuplicateHolidays = String.IsNullOrEmpty(AlreadyExists) ? "date" : "";
var dates = from d in db.Holidays
where d.HolidayDate == startDates && d.PersonId == PersonId
select d;
// <= 0..so if holiday does not already exist
if (dates.Count() <= 0)
{
// holidaysRemaining--;
person.HolidaysRemaining = person.HolidaysRemaining - 1;
Holiday holiday1 = new Holiday();
holiday1.PersonId = PersonId.Value;
holiday1.HolidayDate = startDates;
db.Holidays.AddObject(holiday1);
db.SaveChanges();
//say start date is 10. AddDays(1) will make it 11 then return it to startDates in 'startDates' = startdates,
//but doesnt chage the value of startdates = 'startdates'
}
}
}
startDates = startDates.AddDays(1);
}
finally
{
db.People.Detach();
}
return RedirectToAction("Index");
}

Answer 1

Probably this is the easiest solution.
replace:
person.HolidaysRemaining = person.HolidaysRemaining - 1;
with:
var dbPerson = from p in db.People where p.Id == PersonId select p;
dbPerson[0].HolidaysRemaining--;
Alternatively we were discussing attaching the person object since you have it:
db.People.Attach(person)
try {
// ... loop and everything else here
} finally {
db.People.Detach(person);
}
} // end of method
But this is a bit more brittle, and would only be necessary if there's not already a Person object in db.People.
Note: It seems a little weird that both person and PersonId are passed into listHolidays().

Answer 2

I think your problem is here:
if (dates.Count() <= 0)
{
// holidaysRemaining--;
person.HolidaysRemaining--;
Try changing it to:
if (dates.Count() <= 0)
{
// holidaysRemaining--;
person.HolidaysRemaining = person.HolidaysRemaining - 1;
EDIT
Also, you never actually update the database with person?
db.People.Attach(person);
before db.SaveChanges();
EDIT AGAIN
Try this:
[HttpPost]
public ActionResult listHolidays(Holiday holiday, Person person, int? PersonId, string HolidayDate, string endDate, string AlreadyExists)
{
//int holidaysRemaining = 20;
//person.HolidaysRemaining = holidaysRemaining;
DateTime startDates = Convert.ToDateTime(HolidayDate);
DateTime endDates = Convert.ToDateTime(endDate);
while (startDates <= endDates)
{
if (startDates.DayOfWeek != DayOfWeek.Saturday && startDates.DayOfWeek != DayOfWeek.Sunday)
{
//if user selects Holiday that already exists, wont add it to Db
//gets string, and uses the previously converted to dateTime 'startDate'
//id so only applies to person creating holidays
ViewBag.CantDuplicateHolidays = String.IsNullOrEmpty(AlreadyExists) ? "date" : "";
var dates = from d in db.Holidays
where d.HolidayDate == startDates && d.PersonId == PersonId
select d;
// <= 0..so if holiday does not already exist
if (dates.Count() <= 0)
{
// holidaysRemaining--;
person.HolidaysRemaining = person.HolidaysRemaining - 1;
Holiday holiday1 = new Holiday();
holiday1.PersonId = PersonId.Value;
holiday1.HolidayDate = startDates;
db.Holidays.AddObject(holiday1);
db.People.Attach(person);
db.SaveChanges();
//say start date is 10. AddDays(1) will make it 11 then return it to startDates in 'startDates' = startdates,
//but doesnt chage the value of startdates = 'startdates'
}
}
startDates = startDates.AddDays(1);
}
return RedirectToAction("Index");
}