Db4o Tree structure C#

Question

Hi Everyone

I'm new to db4o and i'm trying to figure out if it's possible to do the following:

public class Page
{ 
    public Guid ID {get;set;}
    public Page Parent {get;set;}
    public IList<Page> Children {get;set;}
    public String Name {get;set;}
    public String Depth {get;set;}
}

When I save the page i have it's parent only. IE

Page p1 = new Page() { 
    ID = Guid.NewGuid(),
    Name = "p1",
    Parent = null
};
Page p2 = new Page() { 
    ID = Guid.NewGuid(),
    Name = "p2",
    Parent = p1
};
Page p3 = new Page() { 
    ID = Guid.NewGuid(),
    Name = "p3",
    Parent = p1
};

When i load up p1 is there anyway to populate the two children??

Answer 1

Well the easiest way to do this is actually to just use the property-call to wire things up. Like this:

public class Page
{ 
    private Page _parent;
    public Page Parent {
        get{return _parent;}
        set{
            value.Children.Add(this);
            this._parent = value;
        }
    }
    public IList<Page> Children {get;set;}

    // omitted the the other properties
}

As soon as you assign a Page-instance to Page.Parent, the Page is in the Page.Children-property.

Is this a solution?

Answer 2

Not sure about DB4O but you should consider using the IComposite pattern for this.

Answer 3

Db4O will load also the collection of children as soon as you load p1 from the datastore, so yes it's possible...