public abstract class MyCollection : CollectionBase {


   // ...


}

public abstract class AbstractCollectionItem {


   // ...


}

//abstract collection item:


public abstract class Fruit : Control {


	// this has these properties, for example:


	public string Name {


		get.. set..


	}


	public string Color {


		get.. set..


	}


}





//Actual collection items:


public class Apple : Fruit {


	// ...


}





public class Orange : Fruit {


	// ...


}








//Now the collection class:


public class Fruits : CollectionBase {


	// Add... Remove...


	


	public Fruit Item(int i) {


		return (Fruit) List[i];


	}


}





//Collection property in my main control:


[


	ParseChildren(true),


	PersistChildren(false)


]


public class FruitBasket : Control


{


	private Fruits _items;


	[


		DesignerSerializationVisibility(DesignerSerializationVisibility.Content),


		PersistenceMode(PersistenceMode.InnerProperty),


		Editor(typeof(FruitBasketItemsEditor), 


			typeof(System.Drawing.Design.UITypeEditor)),


	]


	public Fruits Items 


	{


		get 


		{


			if(_items == null)


				_items = new Fruits();


			return _items;


		}


	}


}





//Now the collection editor:


public class FruitBasketItemsEditor : CollectionEditor 


{


	public FruitBasketItemsEditor(Type type) : base(type)


	{


	}


	protected override Type[] CreateNewItemTypes() 


	{


		return new Type[] {


			typeof(Apple),


			typeof(Orange)


		};


	}


}

public class FruitBasket : Control {


	private Fruits _items;





	[


		DesignerSerializationVisibility(DesignerSerializationVisibility.Content),


		PersistenceMode(PersistenceMode.InnerProperty),


		Editor(typeof(FruitBasketItemsEditor),  typeof(System.Drawing.Design.UITypeEditor)),


		NotifyParentProperty(true)


	]


	public Fruits Items {


		get {


			if(_items == null)


				_items = new Fruits();





			return _items;


		}


	}


}

using System;


using System.Web.UI;


using System.Web.UI.Design;


using System.Web.UI.WebControls;


using System.ComponentModel;


using System.ComponentModel.Design;


using System.Reflection;


using System.Collections;





namespace FruitBasket


{


	//abstract collection item:


	[ ToolboxItem(false) ]


	public abstract class Fruit : Control  {


		// this has these properties, for example:


		string _name, _color;


		public string Color  {


			get { return (_color == null)?string.Empty:_color; }


			set { _color = value; }


		}


		public string Name {


			get { return (_name == null)?string.Empty:_name; }


			set { _name = value; }


		}


	}





	//Actual collection items:


	public class Apple : Fruit {}


	public class Orange : Fruit {}





	//Now the collection class:


	public class Fruits : CollectionBase  {


		public void Add(Fruit i) { List.Add(i); }


		public void Remove(int i) { List.RemoveAt(i); }


		public Fruit Item(int i) {


			return (Fruit) List[i];


		}


	}





	//Collection property in my main control:


	[	ParseChildren(true),


		PersistChildren(false)  ]


	public class FruitBasket : Control {


		private Fruits _items;


		[	DesignerSerializationVisibility(DesignerSerializationVisibility.Content),


			PersistenceMode(PersistenceMode.InnerProperty),


			NotifyParentProperty(true),


			Editor(typeof(FruitBasketItemsEditor), 


				typeof(System.Drawing.Design.UITypeEditor))  ]


		public Fruits Items {


			get {


				if(_items == null)


					_items = new Fruits();


				return _items;


			}


		}


	}





	//Now the collection editor:


	public class FruitBasketItemsEditor : CollectionEditor {


		public FruitBasketItemsEditor(Type type) : base(type) {}


		protected override Type[] CreateNewItemTypes() {


			return new Type[] { typeof(Apple),


						typeof(Orange) };


		}


	}


}

public Fruit this[int index] {


   get {


      return (Fruit)List[index];


   }


}