.NET collection type for storing recent list

Question

Is there a specific collection type in .NET which allows storing a limited number objects and removing the oldest element automatically? What's the easiest way to implement such "Recent Files" functionality?

Answer 1

You might want to try System.Collections.Queue?

Each time before you add an object to your Queue (Enqueue()), you can check the Count to decide if you need the oldest object to be removed (Dequeue()).

Answer 2

You are probably interested in an LRU cache implementation, since a Queue won't give you the easy lookup ability.

EDIT: For just offering "Recent Files" functionality LRU cache would be overkill - go with the simple Queue just like the other poster suggested.

Answer 3

I would go with a class wrapping a linked list. For a quick and dirty example for a starting point see the code below. Of course you will want to add other accessors etc. This will give you the ability to move recently accessed items to the head of the list etc.

public class RecentList<T> : IEnumerable<T>
{
  private LinkedList<T> _list = new LinkedList<T>();
  private int _maxItems;

  public RecentList(int maxItems)
  {
    _maxItems = maxItems;
  }

  public void Add(T item)
  {
    _list.AddFirst(item);
    if (_list.Count > _maxItems)
    {
      _list.RemoveLast();
    }
  }

  public IEnumerator<T> GetEnumerator()
  {
    return _list.GetEnumerator();
  }

  IEnumerator IEnumerable.GetEnumerator()
  {
    return _list.GetEnumerator();
  }
}