Recursive select via LINQ? [duplicate]

Answer 1

I would load the divisions in an non-recursive way and then set up the recursive relations in code. Here is an example, which does this in a lazy way

public class Division
{
    public int ID { get; set; }
    public int DivisionID { get; set; }
    public string Name { get; set; }
    public string Description { get; set; }

    private static List<Division> _divisions;
    public static List<Division> Divisions
    {
        get
        {
            if (_divisions == null) {
                LoadAndSetUpDivisionsHierarchy();
            }
            return _divisions;
        }
    }

    private static Dictionary<int, Division> _divisionsByID;
    public static Dictionary<int, Division> DivisionsByID
    {
        get
        {
            if (_divisionsByID == null) {
                LoadAndSetUpDivisionsHierarchy();
            }
            return _divisionsByID;
        }
    }

    private static Division _root;
    public static Division Root
    {
        get
        {
            if (_root == null) {
                LoadAndSetUpDivisionsHierarchy();
            }
            return _root;
        }
    }

    private Division _parentDivision;
    public Division ParentDivision
    {
        get
        {
            if (_parentDivision == null && DivisionID != 0) {
                _parentDivision = DivisionsByID[DivisionID];

            }
            return _parentDivision;
        }
    }

    private List<Division> _subDivisions = new List<Division>();
    public List<Division> SubDivisions
    {
        get { return _subDivisions; }
    }

    private static void LoadAndSetUpDivisionsHierarchyHierarchy()
    {
        // Load the divisions in a non-recursive way using LINQ
        // (details not shown here).
        _divisions = LoadDivisions();

        // Add the divisions in a dictionary by id
        _divisionsByID = new Dictionary<int, Division>(_divisions.Count);
        foreach (Division division in _divisions) {
            _divisionsByID.Add(division.ID, division);
        }

        // Define sub-divisions and root division
        foreach (Division division in _divisions) {
            if (division.DivisionID == 0) {
                _root = division;
            } else if (division.ParentDivision != null) {
                division.ParentDivision.SubDivisions.Add(division);
            }
        }
    }

    private static List<Division> LoadDivisions()
    {
        throw new NotImplementedException();
    }
}