You typically extend a class by deriving from a base class and enhancing the functionality in the derived class. A new feature in Visual Basic 2008, you extend any existing type's functionality, even when a type is not inheritable.

In the November issue of MSDN Magazine, Adrian "Spotty" Bowles explains how extension methods provide a simple mechanism to extend types in the system with new methods. Extension methods create the illusion that they are defined on a real type, but, in reality, no changes are made to the original types.

And these extension methods play a crucial role in the implementation of LINQ.

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Enjoy!