Specialized Dictionary
Part of my 2008 study notes for exam 70-536 (.NET Framework 2.0).
Overview
- 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.
Good practice
- When possible, use a generic collection instead.
Examples
ListDictionary: Adding and Removing Elements
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: Adding and Removing Elements
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: Adding and Removing Elements
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]); }
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