Array and lazy initializations

Question

Hi,

I have the following problem, I would like to declare an array that will represents the lines of a buffer and foreach item it will hold another list that stores the tokens for this line, something like :

public class TokenArray : List<Token>
{

}

 public List<TokenArray> TokenLines { get; private set; }

When I instantiate my TokenLines array I have to do the following thing :

TokenLines = new List<TokenArray>(lineCount);
for (int i = 0; i < lineCount; i++)
{
     TokenLines.Add(new TokenArray());
}

How can I avoid to instantiate a tokenarray foreach TokenLine ?

Is there a kind of LazyArray<T> that I could use where the TokenArray would be created when I access TokenLines[index] for the first time ?

Thanks

Answer 1

I finally wrote this 

public class LazyArray<T> : List<T>
    {
        private readonly Func<int, T> itemCreator;

        public LazyArray(int count, Func<int, T> itemCreator):base(count)
        {
            this.itemCreator = itemCreator;
        }

        new public T this[int index]
        {
            get
            {
                if (index >= base.Count)
                {
                    for (int i = base.Count; i <= index; i++)
                    {
                        this.Add(this.itemCreator(index));
                    }
                }
                return base[index];
            }
            set
            {
                throw new NotImplementedException();
            }
        }
    }
Func<int, TokenArray> itemCreator = itemCreator = index => new TokenArray(); ;
TokenLines = new LazyArray<TokenArray>(linecount, itemCreator);

and it works but I don' tknow why I am not really satisfied so if you have other idea to solve my problem ...