Question

I have to develop a custom collection of objects. The reason is two fold, I need to be able to assign an internal name to the collection and the collection also needs to implement some abstract methods to be treated like any other entity that I have.

So I created an EntityList class. Below is a snippet of the class. It contains a id and a list of entities, plus a bunch of methods. My question is this, so far I have put in the list management methods that I require, such as Add, Insert, Remove and Clear. If you have an EntityList reference called myEntityList you could perform something like myEntityList.Add(newEntity). I do like this approach, but really these methods are just handing off the work to the list. I could also not implement any of these methods and you could perform the same action as above by using myEntityList.Items.Add(newEntity). However, here you are directly accessing a method of a property of the object. I wanted to remove the Items property altogether, however I often need to iterate through the list using a foreach and for that I need access to the actual list.

Here is my class definition, it does not have the overrides to the abstact methods included.

class EntityList
{
    String entityId;
    List<EntityBase> _entities;

    public EntityList()
    {
        _entities = new List<EntityBase>();
    }

    public List<EntityBase> Items
    {
        get { return _entities; }
        //set { _entities = value; }
    }

    public void Add(EntityBase entity)
    {
        _entities.Add(entity);
    }

    public void Insert(int index, EntityBase entity)
    {
        _entities.Insert(index, entity);
    }

    public void Remove(EntityBase entity)
    {
        _entities.Remove(entity);
    }

    public void Clear()
    {
        _entities.Clear();
    }
}

Am I violating some cardinal rules here? How should I manage the list when it is a member of another class?

Answer 1

Just inherit from List<EntityBase> then you won’t need to redeclare and implement the list methods.

i.e.

class EntityList : List<EntityBase>
{
   String entityId;
   //add your extra methods.
}