Question

Can anybody explain this error message:

The composition remains unchanged. The
changes were rejected because of the
following error(s): The composition
produced a single composition error.
The root cause is provided below.
Review the CompositionException.Errors
property for more detailed
information.

1) No valid exports were found that
match the constraint
‘((exportDefinition.ContractName ==
“Silverbits.ApplicationServices.ApplicationServicesManager”)
AndAlso
(exportDefinition.Metadata.ContainsKey(“ExportTypeIdentity”)
AndAlso
“Silverbits.ApplicationServices.ApplicationServicesManager”.Equals(exportDefinition.Metadata.get_Item(“ExportTypeIdentity”))))’,
invalid exports may have been
rejected.

Resulting in: Cannot set import
‘Silverbits.Applications.SilverbitsApplication.ApplicationServices
(ContractName=”Silverbits.ApplicationServices.ApplicationServicesManager”)’
on part ‘Framework.App’. Element:
Silverbits.Applications.SilverbitsApplication.ApplicationServices
(ContractName=”Silverbits.ApplicationServices.ApplicationServicesManager”)
–> Framwork.App

Answer 1

While the ApplicationServicesManager class may be available and marked with an [Export] attribute, this part may still have been rejected because it has itself imports which cannot be satisfied.

Take a look at the section Diagnosing Composition problems in the MEF documentation.