private static void HashTableTest(IEnumerable<string> words) { var table = new HashTable<string, int>(); foreach (var word in words) { if (table.ContainsKey(word)) { table[word]++; } else { table.Add(word, 1); } } var wordsWithSevenLetters = table.Where(word => word.Key.Length == 7).Select(item => item.Key).ToArray(); foreach (var sevenLetterWord in wordsWithSevenLetters) { table.Remove(sevenLetterWord); } }