Showing data like a tree in code behind

Question

I have a table as listed below

ID   Name   Parent
1     A       0
2     B       1
3     c       1
4     D       2
5     E       2
6     F       0
..    ..      ..

What I need is to show it like

 - A
    -B
     - D
     - E 
    -C

 - F

I am making datatables in c# like

I am getting the data with jquery-ajax and preparing the html from a web method, but I don't want to use any plugin for making the treeview.

Select The records in dtParent where Parent = 0

After this I am trying to filter the records for child entries.

I believe this can be easily done with the recursion but I am not able to find the correct logic.

The code I tried (dtGoals is table where I have all the records and in dtData I am getting only Parents)

dtData = dtGoals;
dtData.DefaultView.RowFilter = "ID = " + dtGoals.Rows[goalCount]["GoalId"].ToString();
dtData.AcceptChanges();
dtData = dtData.DefaultView.ToTable();

After RowFilter Parent records are in dtData. Make the tree node with first record (ID = 1). Now I don't know how to proceed.

Any help will be appreciated.

Thanks in advance.

Answer 1

public class Item
{
    public Item()
    {
        Children = new List<Item>();
    }

    public int Id { get; set; } 
    public string Name { get; set; } 
    public int ParentId { get; set; }
    public List<Item> Children { get; set; } 
}

public class TreeBuilder
{
    public TreeBuilder(IEnumerable<Item> items)
    {
        _items = new HashSet<Item>(items);
        TreeRootItems = new List<Item>();
        TreeRootItems.AddRange(_items.Where(x => x.ParentId == 0));
        BuildTree(TreeRootItems);
    }

    private readonly HashSet<Item> _items;
    public List<Item> TreeRootItems { get; private set; }


    public void BuildTree(List<Item> result)
    {
        foreach (var item in result)
        {
            item.Children.AddRange(_items.Where(x => x.ParentId == item.Id));
            BuildTree(item.Children);
        }
    }
}