[caseymarquis]

While LINQ does include a library of extension methods for functional programming with .NET collections (which is great), it also includes "Expression Classes". In a nutshell, this allows a user to pass a single expression lambda to a function, and the function implementor receives the abstract syntax tree for the lambda, not the lambda itself. You can then not only receive and analyze these trees, you can also manually build and compile them. This effectively allows a limited set of runtime macros within .NET.