How to retrieve recurring costs using Linq - linq

Question

I want to specify when a cost is first incurred and a repeat period in years that means the cost is incurred again and again. So I have created a Cost model that looks like this:
public class Cost
{
public Cost()
{
Year = 1;
}
public decimal Amount { get; set; }
public int AnsweredQuestionID { get; set;}
public virtual AnsweredQuestion AnsweredQuestion {get; set;}
public int? RepeatPeriod { get; set; }
}
Now I want to return the costs incurred between two dates, preferably using Linq.
Edit I oversimplified my question. I have PropertyCosts that are incurred on a specific Date and again after a period of time. The date the cost is first incurred is calculated from the date the property was surveyed. The costs model stores the RepeatPeriod and is related to a specific Question/Answer. The cost is incurred if a question has been answered in a specific way for a property. So I've got code that looks a bit like this (still trying to simplify here) but at the moment I'm only getting the first occurences
public IEnumerable<PropertyCost> GetCosts(DateTime startDate, DateTime endDate)
{
IQueryable<AnsweredQuestion> answeredQuestions =
_Uow.AnsweredQuestionRepository
.All
.Where(x => x.PropertySurvey.PropertyID == id);
IQueryable<Cost> allCosts = UOW.CostRepository.All;
IQueryable<PropertyCost> firstOccurences = from aq in answeredQuestions
from c in costs
where aq.ID == c.AnsweredQuestionID
select new PropertyCost
{
QuestionText = aq.Question.Text,
AnswerText = aq.Answer.Text,
UnitCost = c.Amount,
Date = aq.PropertySurvey.Survey.StartDate,
RepeatYears = c.RepeatPeriod
});
//but now I need to insert PropertyCosts for recurring costs that occur when RepeatPeriod is not null
}

Answer 1

How about this....
var costs = firstOccurences.SelectMany (p =>
from x in Enumerable.Range(0, (p.RepeatYears ?? 0) > 0
? ((endDate.Year - p.Date.Year)+1)/p.RepeatYears.Value
: 1)
let date = p.Date.AddYears(x * p.RepeatYears??0)
where startDate <= date && endDate >= date
select new PropertyCost {
QuestionText=p.QuestionText,
AnswerText=p.AnswerText,
UnitCost = p.UnitCost,
Date = date,
RepeatYears = p.RepeatYears
}
)
You may need to convert firstOccurences to an Enumerable first due to translations functions
eg
IEnumerable<PropertyCost> firstOccurences = (from aq in answeredQuestions
from c in costs
where aq.ID == c.AnsweredQuestionID
select new PropertyCost
{
QuestionText = aq.Question.Text,
AnswerText = aq.Answer.Text,
UnitCost = c.Amount,
Date = aq.PropertySurvey.Survey.StartDate,
RepeatYears = c.RepeatPeriod
}).AsEnumerable();
It's a quick fix and the initial 0 from the Enumerable.Range could be replaced with a calculation.

Answer 2

First of all, I have no idea why would you like to return collection of Cost items. You should create another class to handle that data, e.g.:
public class CostOccurrence
{
public decimal Amount { get; set; }
public DateTime Occurrence { get; set; }
}
And then implement your method:
public IEnumerable<CostOccurrence> GetCosts(DateTime startDate, DateTime endDate)
{
DateTime current = FirstIncurred;
while (current < startDate)
current = current.AddYears(RepeatPeriod);
while (current >= startDate && current < endDate)
{
yield return new CostOccurrence { Amount = Amount, Occurrence = current };
current = current.AddYears(RepeatPeriod);
}
}