(ID/ParentID) list to Hierarchical list

Question

MyClass consists of ID ParentID and List as Children

I have list of MyClass

Answer 1

I have required such functionality and compare both methods and find method 2nd is faster than 1st :), right now in my database cards or records are limited but 1st method taking 4 times more time to complete.

may be this can help for those who are conscious about time.

1 method

---

    public JsonResult CardData()
    {
        var watch = System.Diagnostics.Stopwatch.StartNew();
        OrgChartWithApiContext db = new OrgChartWithApiContext();

        var items = db.Cards.ToList();
        Action SetChildren = null;
        SetChildren = parent => {
            parent.Children = items
                .Where(childItem => childItem.ParentId == parent.id)
                .ToList();

            //Recursively call the SetChildren method for each child.
            parent.Children
                .ForEach(SetChildren);
        };

        //Initialize the hierarchical list to root level items
        List hierarchicalItems = items
            .Where(rootItem => !rootItem.ParentId.HasValue)
            .ToList();

        //Call the SetChildren method to set the children on each root level item.
        hierarchicalItems.ForEach(SetChildren);
        watch.Stop();
        var timetaken = watch.ElapsedMilliseconds;

        return new JsonResult() { Data = hierarchicalItems, ContentType = "Json", JsonRequestBehavior = JsonRequestBehavior.AllowGet };
    }

---

method 2

---

    public JsonResult Card2Data()
    {
        var watch = System.Diagnostics.Stopwatch.StartNew();
        OrgChartWithApiContext db = new OrgChartWithApiContext();
        var items = db.Cards.ToList();
        List topItems = items.Where(item => !item.ParentId.HasValue).ToList();
        topItems.ForEach(item => item.Children = items.Where(child => child.ParentId == item.id).ToList());
        watch.Stop();
        var timetaken = watch.ElapsedMilliseconds;
        return new JsonResult() { Data = topItems, ContentType = "Json", JsonRequestBehavior = JsonRequestBehavior.AllowGet };
    }