The collections in many aspects are similar to the VO arrays, but they differ from them as you need to specify the type of the elements (of course, you can type the elements as object leaving this completely open.

The collections are available in the namespaces

• System.Collections
• System.Collections.Generic
• System.Collections.Concurrent
• System.Collections.ObjectModel
• System.Collections.Specialized

There are a lot of different Collection classes, but the most important are:

• System.Collections.Generic.List<T>
• System.Collections.Generic.Dictionary<TKey,TValue>
• System.Collections.SortedList
• System.Collections.ArrayList

If you need some help, which Collection class to use, here is a help:

• MSDN: Selecting a collection class
• MSDN: Commonly used collection types

But it is very important to know that you cannot change a collection while you are using it in a foreach loop.