Question

UPDATE: The initial idea was to nest the objects, but I then realised that having an ancestry trail in each object would suffice, so the title has been amended.

I want to build up a collection of objects which I can play with while developing (the idea will be to put them into a MongoDB collection) but can’t figure out how to do the multiple depths.

The objects for this scenario have only a name, an id (auto incrementing), and a forward slash delimited string of each object’s parents.

I have managed to get the initial recursion working:

id Ancestors Name

1
/
LFHVJULLCA

2
/1/
OHOEKOOFZP

3
/1/2/
PIUHBACFJV

4
/1/2/3/
PYKUFZOHXS

5
/1/2/3/4/
UJFUYENSQV

6
/1/2/3/4/5/
SHLMWCKZUJ

7
/1/2/3/4/5/6/
SFBHLQXTZL

8
/1/2/3/4/5/6/7/
AHHHUGDZIX

9
/1/2/3/4/5/6/7/8/
MKOODIMYXC

10
/1/2/3/4/5/6/7/8/9/
OONOZOHYJH

but what I want is to have a second or third level of ancestry, so that each item can have further children, updating its ancestry, and adding itself to the main collection.

And that is where I’m stuck. Any pointers please?

List<Thing> things;
int count;

void Main()
{
    things = new List<Thing>();

    count = 1;
    int depth = 10;
    int thingsPerThing = 3;

    var thing = new Thing{ Ancestors = "/", id = count++, Name = "Name " + count};
    things.Add(thing);

    AddThing(depth, 0, thingsPerThing, thing);

    things.Dump();
}

public class Thing
{
  public int id{get;set;}
  public string Ancestors{ get;set;}
  public string Name{get;set;}
}

public void AddThing( int depth, int CurrentDepth, int thingsPerThing, Thing thing)
{
    CurrentDepth++;
    if( CurrentDepth < depth )
    {
        var newThing = CreateThing(thing);
        things.Add( newThing );
        AddThing( depth--, CurrentDepth, thingsPerThing, newThing);
    }

}

public Thing CreateThing(Thing thing)
{
    return new Thing{ Ancestors = thing.Ancestors + thing.id + "/", id = count++, Name = RandomString(10) };
}

Answer 1

You should use a Tree collection.

Some examples of implementation:
– An Extensive Examination of Data Structures Using C# 2.0 (MSDN)
– Implementing a Non-Binary Tree in C# (Dan Vanderboom’s blog)
– A Generic Tree Collection (CodeProject)

To get the full path of a node you can add a Path property which walk backward to its root. To get the list of nodes (if needed) you have to implement a tree traversal algorithm, you can do it in many ways, which one to use depends on the order you want for your nodes (see link for details).

If you need a more sophisticated library for collection you may consider to check these:
– The C5 Generic Collection Library
– Wintellect’s Power Collection