public static void Main() { // Create HashTable and add few elements. var hashtableTest = new HashTable<int, string>(); hashtableTest.Add(1, "One"); hashtableTest.Add(11, "Eleven"); hashtableTest.Add(2, "Two"); hashtableTest.Add(3, "Three"); Console.WriteLine("---------- Test Find(1) ----------"); Console.WriteLine(hashtableTest.Find(1)); Console.WriteLine("\n---------- Test Remove(1) ----------"); hashtableTest.Remove(1); Console.WriteLine("\n---------- Test Count() ----------"); Console.WriteLine(hashtableTest.Count()); Console.WriteLine("\n---------- Test get all Keys() and print ----------"); var listOfKeys = hashtableTest.Keys(); foreach (var item in listOfKeys) { Console.WriteLine(item); } Console.WriteLine("\n---------- Test foreach ----------"); foreach (var item in hashtableTest) { Console.WriteLine(item); } // If index is empty this will throw new NullReferenceException. Console.WriteLine("\n---------- Test this[0] ----------"); Console.WriteLine(hashtableTest[2]); Console.WriteLine("\n---------- Test Clear() and print count ----------"); hashtableTest.Clear(); Console.WriteLine(hashtableTest.Count()); }