Specialized Dictionary

• Special case dictionaries
• ListDictionary
  • Used as a HashTable for fewer than 10 items.
  • Implemented as a simple linked list behind the scenes.
  • Same interface as HashTable, easy to replace.
• HybridDictionary
  • Used as a HashTable for unknown sizes of items.
  • Implemented as a combination between HashTable and ListDictionary.
  • Switches over to a HashTable when the collection becomes too big.
  • Same interface as HashTable, easy to replace.
• OrderedDictionary
  • Used as a HashTable when you need access to the index.
  • A plain dictionary mapping, like a cross between HashTable and ArrayList.

• When possible, use a generic collection instead.

ListDictionary a = new ListDictionary();
a.Add("Key2", "Hello");
a.Add("Key1", "World");
a.Add("Key0", "Start");
 
Console.WriteLine(a["Key1"] + " " + a["Key2"]);
Console.WriteLine();
foreach (DictionaryEntry d in a) { Console.WriteLine(d.Value); }
Console.WriteLine();
foreach (var v in a.Values) { Console.WriteLine(v); }
Console.WriteLine();
a.Remove("Key1");
foreach (var k in a.Keys) { Console.WriteLine(a[k]); }

HybridDictionary a = new HybridDictionary();
a.Add("Key2", "Hello");
a.Add("Key1", "World");
a.Add("Key0", "Start");
 
Console.WriteLine(a["Key1"] + " " + a["Key2"]);
Console.WriteLine();
foreach (DictionaryEntry d in a) { Console.WriteLine(d.Value); }
Console.WriteLine();
foreach (var v in a.Values) { Console.WriteLine(v); }
Console.WriteLine();
a.Remove("Key1");
foreach (var k in a.Keys) { Console.WriteLine(a[k]); }

OrderedDictionary a = new OrderedDictionary();
a.Add("Key1", "Hello");
a.Add("Key2", "World");
a.Add("Key0", "Start");
a.Insert(1, "Key10", "Inserted");
 
Console.WriteLine(a["Key1"] + " " + a["Key2"]);
Console.WriteLine();
foreach (DictionaryEntry d in a) { Console.WriteLine(d.Value); }
Console.WriteLine();
foreach (var v in a.Values) { Console.WriteLine(v); }
Console.WriteLine();
a.Remove("Key1");
a.RemoveAt(0);
foreach (var k in a.Keys) { Console.WriteLine(a[k]); }