Managed Extensibility Framework (MEF) is a component of .NET Framework 4.0 aiming to create lightweight, extensible applications. It aims to allow .NET application developers to discover and use extensions with no configuration required. It also aims to let extension developers encapsulate code easily and avoid fragile hard dependencies. Furthermore, it aims to allow extensions to be reused across applications. MEF was introduced as a part of .NET 4.0 and Silverlight 4.