To customize the default behavior for an export in the https://learn.microsoft.com/en-us/dotnet/framework/mef/[Managed Extensibility Framework] (MEF), applying the https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.composition.partcreationpolicyattribute[`PartCreationPolicyAttribute`] is necessary.
For the https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.composition.partcreationpolicyattribute[`PartCreationPolicyAttribute`] to be meaningful in the context of an export, the class must also be annotated with the https://learn.microsoft.com/en-us/dotnet/api/system.componentmodel.composition.exportattribute[`ExportAttribute`].