arraylist of integer array

[iemrgh]

Hi
I'm wondering if anyone can help me about this problem:
I want to make two dimension integer array but the number of rows isn't determined,so I tried arraylist.In this case I don't know how to declare and what to do when I want to retrieve the inserted data like which was in 2d arrays (like integerarray{i][j]).
Thanks...

[Christian Binder]

Hi!
You could create your own class and take usage of the this[]-Property/Indexer.

I've made a little default implementation ...

public class MyArray<T> {
    public Dictionary<int, T> _list { get; set; }
    private T _default;
 
    public T this[int index] {
      get{
        if (_list == null || !_list.ContainsKey(index))
          return _default;
        return _list[index];
      }
 
      set{
        if (_list == null)
          _list = new Dictionary<int, T>();
 
        if (_list.ContainsKey(index))
          _list[index] = value;
        else
          _list.Add(index, value);
      }
    }
  }
 

And you can use this class that way:

 
MyArray<MyArray<int>> integerarray = new MyArray<MyArray<int>>();
integerarray[1][1] = 10;
 

I hope this works, I haven't tested it yet :-)

[jkmyoung]

Not sure that helps. Thought the point was to be able to add and resize the array.

            ArrayList al = new ArrayList();
 
 
            for (int i = 0; i < 10; i++)
            {
                al.Add(new int[10]);
            }
 
            int av = ((int[])(al[3]))[2];
 

The accessing with your current method is somewhat ugly, since you have to cast the temporary result to an int[].

I think you probably want a List<int[]> instead: eg

            List<int[]> intList = new List<int[]>();
            for (int i = 0; i < 10; i++)
            {
                intList.Add(new int[10]);
            }
            int av = intList[3][2];
 

You have to know the number of columns beforehand, unless you want to use an List of List<int>.