Question

Let’s say we have a Windows app that has a TreeView and you can expand the nodes of this view and drill down to the children node, they may also have more children so now we can expand that node and go further, etc.. So in my source code I have a method Foo(string fatherNode) that gets the father node that we clicked on and finds the children and lists them:

the high level body of this method is like this:

private void Foo(string fatherNode)
{
  // call some DB scripts and grab data you need to work with.
  int numberOfKids = // get it from the thing you populated from the DB call.
  for(int i = 1  to numberOfKids)
  {
     Node Child = // grab child[i] from the list we populated from DB calls
     //Add it to the treeView
  }
}

Well that code is good for a UI app, where we click on a node, it runs this method once and collects the data it needs, Now I need to write another method utilizing useful lines of the method above Grab EVERYTHING at once and write the Whole information to let’s say a file.

So in my head in looks like a recursive method to me. But still can’t figure out the whole picture, Prob should have two collections, one for fathers, one for kids, loop through kids and make recursive call to get more kids and add them to the collection, etc

I was wondering if you can clear out the fogs, the high-level of what I need to do to, how the colections should look like, where to add to them, where to call the recursive method call, etc…and please don’t specifically think about a “treeview” object, I just used that as an example to expalin the question better. The main thing is the structure of the Foo method that I posted. That’s what I should work with.

Answer 1

Well, I’m not sure if this is what you’re looking for, even after the other answers.
However, please, check it out:

The self-related entity (Node)

public class MyEntity
{
    public MyEntity() { }

    public MyEntity(string Name, int ID, int? ParentID)
    {
        this.Name = Name;
        this.ID = ID;
        this.ParentID = ParentID;
    }

    public string Name { get; set; }
    public int ID { get; set; }
    public int? ParentID { get; set; }
}

The tree building methods

    public static StringBuilder GetFamilyTree(List<MyEntity> AllTheEntities)
    {
        StringBuilder Return = new StringBuilder();

        List<MyEntity> OrderedEntities = AllTheEntities.OrderBy<MyEntity, int>(x => x.ID).ToList();

        foreach (MyEntity CurrentEntity in AllTheEntities.Where<MyEntity>(x => !x.ParentID.HasValue))
        {
            Return.AppendLine(GetEntityTree(AllTheEntities, CurrentEntity));
        }

        return Return;
    }

    public static string GetEntityTree(List<MyEntity> AllTheEntities, MyEntity CurrentEntity, int CurrentLevel = 0)
    {
        StringBuilder Return = new StringBuilder();

        Return.AppendFormat("{0}{1}", "\t".Repeat(CurrentLevel), CurrentEntity.Name);
        Return.AppendLine();

        List<MyEntity> Children = AllTheEntities.Where<MyEntity>(x => x.ParentID.HasValue && x.ParentID.Value == CurrentEntity.ID).ToList();

        if (Children != null && Children.Count > 0)
        {
            foreach (MyEntity CurrentChildEntity in Children)
            {
                Return.Append(GetEntityTree(AllTheEntities, CurrentChildEntity, CurrentLevel + 1));
            }
        }

        return Return.ToString();
    }

A small helper class

public static class StringExtension
{
    public static string Repeat(this string text, int times)
    {
        string Return = string.Empty;

        if (times > 0)
        {
            for (int i = 0; i < times; i++)
            {
                Return = string.Concat(Return, text);
            }
        }

        return Return;
    }
}

Usage

        List<MyEntity> AllMyEntities = new List<MyEntity>();
        AllMyEntities.Add(new MyEntity("1", 1, null));
        AllMyEntities.Add(new MyEntity("1.1", 2, 1));
        AllMyEntities.Add(new MyEntity("1.1.1", 3, 2));
        AllMyEntities.Add(new MyEntity("2", 4, null));
        AllMyEntities.Add(new MyEntity("2.1", 5, 4));

        Console.Write(GetFamilyTree(AllMyEntities).ToString());

Results

1
    1.1
        1.1.1
2
    2.1