HashSet<T> is a generic collection with the following features:
HashSet<T> is implemented with a hashtable.
HashSet<T> implements ICollection<T> and offers methods such as Contains, Add, and Remove.
HashSet<T> has a predicate-based removal method called RemoveWhere.
The following code creates a HashSet<char> from an existing collection.
Then it uses Contains method to check if the element is in.
using System; using System.Collections.Generic; class MainClass//from w ww . j av a2 s. co m { public static void Main(string[] args) { var letters = new HashSet<char> ("the quick brown fox this is atest "); Console.WriteLine (letters.Contains ('t')); // true Console.WriteLine (letters.Contains ('j')); // false foreach (char c in letters) Console.Write (c); } }