C# has a number of Collection classes including:

interface      class
IList          ArrayList
IList          StringCollection
IDictionary    Hashtable
IDictionary    SortedList

Here are some comparisons with classes from Java's Collections API:

C#             Java
ArrayList      ArrayList
N/A            LinkedList
N/A            HashSet
N/A            TreeSet
Hashtable      HashMap
SortedList     TreeMap