LINQKit

LINQKit is a free set of extensions for LINQ to SQL power users. It comprises the following:

* An extensible implementation of AsExpandable()
* A public expression visitor base class (ExpressionVisitor)
* PredicateBuilder
* Linq.Expr and Linq.Func shortcut methods

With LINQKit, you can:

* Plug expressions into EntitySets
* Use expression variables in subqueries
* Combine expressions (have one expression call another)
* Dynamically build predicates
* Leverage AsExpandable to add your own extensions.


http://www.albahari.com/nutshell/linqkit.aspx