C# 5.0 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:

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var tbl = new Hashtable();tbl.Add("Bart", 29);tbl["John"] = 64;bool bartIsKnown = tbl.ContainsKey("Bart");bool someIsAged64 = tbl.ContainsValue(64);foreach (string name in tbl.Keys)    Console.WriteLine("Age of {0} is {1}", name, tbl[name]);tbl.Remove("Bart");

Internally, keys are hashed by making a virtual method call to the key’s GetHashCode implementation. The idea of a hash code is to provide an integer value for an object with as good uniqueness properties as possible. Whenever an entry is requested from the table ...