CODEWITHSUNDEEP
c#asp.net-mvclinq
Kman
Kman

Reputation: 5001

linq conditional query

What would be the best practice for setting a status depending on several other "columns" retrieved in a linq query. 

  var result = (from q in query
                select new Item
                         {
                           ApprovedDate = q.ApprovedDate,
                           CreatedDate = q.CreatedDate,
                           DeclinedDate = q.DeclinedDate,
                           Status = 0
                         });

I'd like to set the status to either 0, 1, 2.

(ApprovedDate == null and DeclinedDate == null) --> 0
(ApprovedDate != null and DeclinedDate == null) --> 1
(DeclinedDate != null) --> 3

So perhaps something like:

  var result = (from q in query
                select new Item
                         {
                           ApprovedDate = q.ApprovedDate,
                           CreatedDate = q.CreatedDate,
                           DeclinedDate = q.DeclinedDate,
                           Status = (q.CreatedDate == null && q.DeclinedDate == null) ? 0 : (q.ApprovedDate != null && q.DeclinedDate == null) ? 1 : 2
                         });

I might add even more status combinations, so should I try and do this in the linq select query, in my repository object.. Or later on in the controller where I would do a .ToList() and then foreach the list to set the correct status code?

Having even more than 3 statuscodes, the linq query gets "hard" to read.

Upvotes: 1

Views: 1067

Answers (2)

Sergey Berezovskiy
Sergey Berezovskiy

Reputation: 236308

What about moving status calculation to Item class? If status property depends on other properties value, then it's definitely calculated property:

var result = from q in query
             select new Item
                         {
                           ApprovedDate = q.ApprovedDate,
                           CreatedDate = q.CreatedDate,
                           DeclinedDate = q.DeclinedDate
                         });

And

public class Item
{
  // other properties

  public int Status
  {
      get
      {
          if (ApprovedDate == null and DeclinedDate == null)
              return 0;
          if (ApprovedDate != null and DeclinedDate == null)
              return 1;
          if (DeclinedDate != null)
              return 3;
          // etc
      }
  }
}

Actually I think it's best option, because in this case status calculation logic will be close to required data. If (for some reason) you can't use this approach, then move setting statuses to local items collection:

var items = result.ToList().ForEach(i => i.Status = CalculateStatus(i));

Upvotes: 2

Jorge
Jorge

Reputation: 18257

Maybe wrapped all in a function An do a linq like this

var result = (from q in query sele q).AsEnumerable()
                                       .Select( x => new Item()
                                       {
                                           ApprovedDate = x.ApprovedDate,
                                           CreatedDate = x.CreatedDate,
                                           DeclinedDate = x.DeclinedDate,
                                           Status = MyStatusFunction(x.CreatedDate,q.DeclinedDate)
                                       });


public int MyStatusFunction(DateTime ApprovedDate , Datetime DeclinedDate)
{
    if (ApprovedDate == null and DeclinedDate == null) return 0;
    else if(ApprovedDate != null and DeclinedDate == null) return 1;
    else if (DeclinedDate != null) return 3;
}

Upvotes: 0

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