proper way to store unknown number of object instances?

Question

What is the proper way (or any way) to store the reference to an unknown number of object instances in C#? Let say I have a class called Widget and I want to make a lot of instances of Widget and keep track of them all the number of them depending on how many a user needs/creates. If I store all the instance references in an array I have to declare ahead of time how many there are so that doesn't seem to work. I'm used to languages that allow me to just add dynamically to an existing array so I don't have to worry about how many of something I am going to store. How do I do this in C#? Sorry for a question so basic.

wadeontheweb · Answer

Cool! Thanks for the help!

john_farrellus · Answer

Errata: I accidently said the  CollectionBase  is in the System.Configuration namespace but it's really in the  System.Collections  namespace. The sample code had it right. Must get another cup of coffee this morning and wake up.

john_farrellus · Answer

There are many ways to do this... Arraylist works fine. My prefered method is to make a Collection Object. Make another class I usually call it (Class name) + Col so for you WidgetsCol. My preference is to generally keep as much code out of the Form (User Interface) layer as possible and put it all into classes to maximize code reuse which is why I build a collection class. Probably looks like more work but it's really not especially if you make an abstract class that all your collection classes inherit. Then inherit  CollectionBase  which is in the  System.Configuration  name space. This will give you access to List in your new object that has a bunch of collection methods to it; Add Count Insert Remove. You then write public methods/properties to expose those them publically or what ever. Here would be a sample start for such an item. If you place the cursor on CollectionBase in the IDE and hit F1 you'll get all sorts of informtion on how you can strong type the collection the events and more usefull stuff. using System; using System.Collections; namespace sample { /// /// Summary description for WidgetsCol. /// public class WidgetsCol : CollectionBase { public WidgetsCol() { } public new int Count { get { return List.Count; } } public void Add(Widget item) { List.Add(item); } public Widget this[int index] { get { return (Widget) List[index]; } set { List[index] = value; } } } public class Widget { private Guid mWidgetID = Guid.NewGuid(); public Widget() { } public Guid WidgetID { get { return mWidgetID; } } } } And a little sample interface for it: private void Form1_Load(object sender System.EventArgs e) { WidgetsCol oWidgets = new WidgetsCol(); oWidgets.Add(new Widget()); oWidgets.Add(new Widget()); Console.WriteLine(oWidgets.Count.ToString()); foreach(Widget widget in oWidgets) Console.WriteLine(widget.WidgetID.ToString()); Widget WidgetItem = (Widget)oWidgets[1]; Console.WriteLine(WidgetItem.WidgetID.ToString()); } And if you want to make the collection class bindable here is a great article: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnadvnet/html/vbnet02252003.asp

wadeontheweb · Answer

The answer is to use an arrayList. Somehow I managed to forget about those. :o)