Normalize objects using linq

Question

I have an IEnumerable<RuleSelection> with these properties:

public class RuleSelection{
  public int RuleId { get; set;}
  public int? CriteriaId { get; set; }
  public int? CriteriaSourceId{ get; set; }
}

RuleId in RuleSelection is not unique.

Can I write a linq query to normalize these into IEnumerable<Rule> which would be:

public class Rule{
  public int RuleId { get; set; }
  public IEnumerable<int> Criteria { get; set; }
  public IEnumerable<int> CriteriaSource { get; set; }
}

Rule.RuleId would be unique and the properties Criteria and CriteriaSource would include all the CriteriaId's and CriteriaSourceId's for the RuleId respectively.

Answer 1

It sounds like you want something like:

var rules = selections.GroupBy(rs => rs.RuleId)
                      .Select(g => new Rule {
                                  RuleId = g.Key,
                                  Criteria = g.Select(rs => rs.CriteriaId)
                                              .Where(c => c != null)
                                              .Select(c => c.Value)
                                              .ToList(),
                                  CriteriaSource = g.Select(rs => rs.CriteriaSourceId)
                                                    .Where(c => c != null)
                                                    .Select(c => c.Value)
                                                    .ToList(),
                              });