C# Dictionary Collection

A Dictionary object in C# has become one of my recent favorites. Below are a few important aspects:

1. Requires including System.Collections.Generic;
2. Each entry in a Dictionary is a KeyValuePair (consisting of two objects: key and value)
3. The key must be unique
4. The value does not need to be unique
5. Both the key and value can be any object (string, int, custom class, etc…)
6. Retrieving a value via a key take close to O(1) time
7. The order of a KeyValuePair enumeration is not defined