Iterator Design Pattern Example

Aggregate.cs

using System;
using System.Collections;
using System.Collections.Generic;

namespace IteratorPattern
{
    //Aggregate
    public abstract class Aggregate
    {
        public abstract Iterator GetIterator();
    }
}

ConcreteAggregate.cs

using System;
using System.Collections;
using System.Collections.Generic;

namespace IteratorPattern
{
    //ConcreteAggregate
    public class MyObjectCollection : Aggregate
    {
        private ArrayList myList = new ArrayList();

        public override Iterator GetIterator()
        {
            return new MyIterator(this);
        }
        public object this[int index]
        {
            get { return myList[index]; }
        }
        public int Count
        {
            get { return myList.Count; }
        }
        public void Add (object obj)
        {
            myList.Add(obj);
        }
    }
}

ConcreteIterator.cs

using System;
using System.Collections;
using System.Collections.Generic;

namespace IteratorPattern
{
//ConcreteIterator
    public class MyIterator : Iterator
    {
        private MyObjectCollection aggregate;
        int index;
        public MyIterator(MyObjectCollection aggr)
        {
            this.aggregate = aggr;
            index = 0;
        }
        public object CurrentItem()
        {
            return aggregate[index];
        }
        public object First()
        {
            return aggregate[0];
        }
        public bool IsDone()
        {
            return index >= aggregate.Count ;
        }
        public object Next()
        {
            object retVal = null;
            if (index < aggregate.Count)
                retVal = aggregate[index++];
            return retVal;
        }
    }
}

Iterator.cs

using System;
using System.Collections;
using System.Collections.Generic;

namespace IteratorPattern
{
    //Iterator
    public interface Iterator
    {
        object First();
        object Next();
        object CurrentItem();
        bool IsDone();
    }
}

Program.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace IteratorPattern
{
    class Program
    {
        //Client
        static void Main(string[] args)
        {
            //MyCollection coll = new MyCollection();
            //foreach(var item in coll)
            //    Console.WriteLine(item.ToString());

            //Create myObject collection and items to it.
            MyObjectCollection aggr = new MyObjectCollection();
            aggr.Add(10);
            aggr.Add(-20);
            aggr.Add("Test");
            aggr.Add(33);
            aggr.Add("Iterator");
            aggr.Add(52.6);

            //Get Iterator and iterator all items
            Iterator itor = aggr.GetIterator();
            while (!itor.IsDone())
            {
                Console.WriteLine(itor.CurrentItem().ToString());
                itor.Next();
            }
            Console.ReadLine();
        }
    }
}