C# 4.0 Unleashed

Hash Tables

A hash table provides key/value pairing with support for efficient lookup by key. Being nongeneric, key and value are represented as System.Object. An exploratory example is shown here:

var tbl = new Hashtable();tbl.Add("Bart", 26);tbl["John"] = 62;bool bartIsKnown = tbl.ContainsKey("Bart");bool someIsAged62 = tbl.ContainsValue(62);foreach (string name in tbl.Keys)    Console.WriteLine("Age of {0} is {1}", name, tbl[name]);tbl.Remove("Bart");

Internally, keys are hashed by use of the key type’s GetHashCode implementation. The idea of a hash code is to provide an integer-valued identifier for an object with as good uniqueness properties as possible. Whenever an entry is requested from the table by using a key, the hash code of the ...