Linq query for the Multi list in singe out put

Question

i have table looks like below

ID | Reason | PrID
----------------- 
1   abc      null
2   dhe      null
3   aerc      1
4   dwes      2
5   adfje     1

i have class

 public class Reason
{
    public int Id { get; set; }
    public string Reson{ get; set; }
    public List<SecondryReason> SecReason{ get; set; }
    public int? PrimaryId { get; set; }
}
public class SecondryReason
{
    public int Id { get; set; }
    public string Reason { get; set; }
    public int PrimaryReasonId { get; set; }
}

I want this to be displayed in hierarchy level if the prid is Null need to treat this as the parent remaining all child

i am trying Linq and unable to achieve this

Suggest me how to do this in an easy way in linq

How does the data comes out of the table? as the Object Reason? or Secondary? Or object array? — Malior, Mar 05 '19 at 14:13
Edit the question please, ReasonName is replicated as Reson? It's difficult to assume and relate table column names and their alias in the class below. — Incredible, Mar 05 '19 at 14:22
you might need to use `Common Table Expression`. See this [answer](https://stackoverflow.com/a/11929928/9534819) — Matt.G, Mar 05 '19 at 14:42

Malior · Accepted Answer · 2019-03-05T15:44:25.220

So: You have a list/enumerable of type , whereof the SecReason List property is null. Then, using linq you want a list, were the only the "root" reasons remain, but the Sub-reasons got put in the lists, but as type SecondaryReason? If so, I found this way to do it (linq and foreach):

    static IEnumerable<Reason> GetReasonsGrouped(List<Reason> reasons)
    {
        var result = reasons.Where(x => x.PrimaryId == null);
        foreach (var item in result)
        {
            item.SecReason = reasons.Where(x => x.PrimaryId == item.Id)
                                    .Select(x => new SecondryReason()
                                                      { Id = x.Id,
                                                        ReasonName = x.ReasonName,
                                                        PrimaryReasonId = item.Id
                                                       })
                                    .ToList();
        }

        return result;
    }

Or just linq, but harder to read:

  var result = reasons.Where(x => x.PrimaryId == null)
            .Select(x =>
            {
                x.SecReason = reasons.Where(r => x.PrimaryId == x.Id)
                                     .Select(r => new SecondryReason()
                                     {
                                         Id = r.Id,
                                         ReasonName = x.ReasonName,
                                         PrimaryReasonId = x.Id
                                     })
                                     .ToList();
                return x;
            });

Thank you so much .. it helps me @Malior – Satti Mar 06 '19 at 11:36 — Satti, Mar 06 '19 at 11:36

score 1 · Answer 2 · answered Mar 06 '19 at 06:58

Not sure if linq will be the best solution, here is my proposed changes and method to get an Hierarchy type:

public class Reason
{
  public int Id { get; set; }
  public string Reson { get; set; }
  public List<Reason> SecReason { get; set; }
  public int? PrimaryId { get; set; }

  //Adds child to this reason object or any of its children/grandchildren/... identified by primaryId
  public bool addChild(int primaryId, Reason newChildNode)
  {
    if (Id.Equals(primaryId))
    {
      addChild(newChildNode);
      return true;
    }
    else
    {
      if (SecReason != null)
      {
        foreach (Reason child in SecReason)
        {
          if (child.addChild(primaryId, newChildNode))
            return true;
        }
      }
    }
    return false;
  }

  public void addChild(Reason child)
  {
    if (SecReason == null) SecReason = new List<Reason>();
    SecReason.Add(child);
  }

}

private List<Reason> GetReasonsHierarchy(List<Reason> reasons)
{
  List<Reason> reasonsHierarchy = new List<Reason>();

  foreach (Reason r in reasons)
  {
    bool parentFound = false;
    if (r.PrimaryId != null)
    {
      foreach (Reason parent in reasonsHierarchy)
      {
        parentFound = parent.addChild(r.PrimaryId.Value, r);
        if (parentFound) break;
      }
    }
    if (!parentFound) reasonsHierarchy.Add(r);
  }
  return reasonsHierarchy;
}

Linq query for the Multi list in singe out put

2 Answers2