This sample shows a simple custom collection implementation in C# with the .NET Framework.
using System;
using System.Collections;
namespace Personal.Demos.Simple{
public class MainApp{
//entry point 'Main'
public static void Main(){
//get us some Widgets
Widgets MyWidgets = Initialize();
Console.WriteLine("Using 'foreach' - ");
//enumerate through the collection with
//the foreach constuct.
foreach(Widget W in MyWidgets){
//call the same method on each item in
//the collection.
Console.WriteLine(W.AMethod());
}
Console.WriteLine("Using 'Indexers' - ");
//enumerate through the collection with
//it's indexer.
for(int i=0; i < MyWidgets.Count ; i++){
//call the same method on each item in
//the collection.
Console.WriteLine(MyWidgets[i].AMethod());
}
}
//fill up a 'Widgets' collection with...
//...well some Widgets.
private static Widgets Initialize(){
Widgets colWidgets = new Widgets();
Widget objWidget;
int i;
for(i=0 ; i < 10 ; i++){
objWidget = new Widget();
objWidget.Number=i;
colWidgets.Add(objWidget);
}
return colWidgets;
}
}
//*****************************************************
//the individual Widget class
public class Widget{
public int Number=0;
public virtual string AMethod(){
return "This Widget's Number is : "
+ Number.ToString();
}
}
//*****************************************************
//Widgets collection class MUST derive from
//System.Collections.CollectionBase
public class Widgets:CollectionBase{
public virtual void Add(Widget NewWidget){
//forward our Add method on to
//CollectionBase.IList.Add
this.List.Add(NewWidget);
}
//this is the indexer (readonly)
public virtual Widget this[int Index]{
get{
//return the Widget at IList[Index]
return (Widget)this.List[Index];
}
}
}
//*****************************************************
}
