This namespace provides classes that constitute the core of the Managed Extensibility Framework, or MEF. Commonly Used Types: System.ComponentModel.Composition.ChangeRejectedException System.ComponentModel.Composition.CompositionContractMismatchException System.ComponentModel.Composition.CompositionError System.ComponentModel.Composition.CompositionException System.ComponentModel.Composition.ExportAttribute System.ComponentModel.Composition.ImportAttribute System.ComponentModel.Composition.ImportCardinalityMismatchException System.ComponentModel.Composition.Hosting.AggregateCatalog System.ComponentModel.Composition.Hosting.ApplicationCatalog System.ComponentModel.Composition.Hosting.AssemblyCatalog System.ComponentModel.Composition.Hosting.CompositionContainer System.ComponentModel.Composition.Primitives.ComposablePartException System.ComponentModel.Composition.Primitives.ExportDefinition System.ComponentModel.Composition.Primitives.ImportDefinition System.ComponentModel.Composition.ReflectionModel.ReflectionModelServices