This namespace provides classes that constitute the core of the Managed Extensibility Framework, or MEF. Commonly Used Types: System.ComponentModel.Composition.Registration.RegistrationBuilder System.ComponentModel.Composition.Registration.PartBuilder System.ComponentModel.Composition.Registration.PartBuilder<T> System.ComponentModel.Composition.Registration.ParameterImportBuilder System.ComponentModel.Composition.Registration.ImportBuilder System.ComponentModel.Composition.Registration.ExportBuilder