Hash set in c#

Although a HashSet is a list of elements, it does not inherit the IList interface. Instead it just inherits the ICollection interface. What this means is elements inside a HashSet cannot be accessed through indices, only through an enumerator (which is an iterator).

Additionally, since a C#.NET HashSet is modeled after a mathematical set, certain functions were implemented such as Union, Intersection, IsSubsetOf, IsSupersetOf. These can come in handy when working with multiple sets.

A resulting difference between a HashSet and a List is that the HashSet's Add method is a boolean function, which returns true of an element was added and false if it wasn't (because it was not unique).

HashSet<int> mySet = new HashSet<int>();
mySet.Add(3);
mySet.Add(5);
mySet.Add(3);
mySet.Add(10);

List<int> myListFromSet = mySet.ToList<int>();
int myInt = myListFromSet[2];