using System.Collections.Generic;
public static class ExtensionExample
public static bool ContainsDuplicates<T>(this IEnumerable<T> collection, HashSet<T> hashSet)
foreach (var item in collection)
private static readonly HashSet<int> m_cachedHashSet = new HashSet<int>();
public static void Main()
var uniqueArray = new int[] {0, 1, 2, 3, 4, 5};
var nonUniqueArray = new int[] {0, 1, 2, 3, 4, 5, 4, 3, 2, 1};
Console.WriteLine(uniqueArray.ContainsDuplicates(m_cachedHashSet));
Console.WriteLine(nonUniqueArray.ContainsDuplicates(m_cachedHashSet));