The namespace contains classes, interfaces and enumerations that enable language-level code expressions to be represented as objects in the form of expression trees.

The abstract class provides the root of a class hierarchy used to model expression trees. The classes in this namespace that derive from , for example and , are used to represent nodes in an expression tree. The class contains static (Shared in Visual Basic) factory methods to create expression tree nodes of the various types. The enumeration type specifies the unique node types.