I have 2 MEF components. Let it be component A and component B.
What I need is to be able to access a class from component B in component A without referencing to it. Then I would like to instantiate object of the class manually.
Currently I see MEF allows instantiating an object automatically using [Import]. It uses interface which requires to be referenced to.
Can I use data types from another assemblies without referencing to it? Is there such mechanism supported by MEF?
There are a couple of ways to do this.
First, you need to define a common interface that both assemblies understand. This could be a "PublicInterfaces" library that both of these assemblies reference, or it could be inside of assembly A (B references A, but not the other way around).
In B, export the type using this interface.
B has to be in the container's catalog. Either reference assembly B explicitly in an AssemblyCatalog
, or create a DirectoryCatalog
and point it at the directory that will contain assembly B.
In A, instead of using Import attributes, in code call GetExportedValue<T>()
on the container. The code looks something like this:
// Known by A and B
public interface CommonInterface
{
// ...
}
// In B, not A
[Export(typeof(CommonInterface))]
public class BClass : CommonInterface
{
// ...
}
// In A where you want to manually create class B
CommonInterface objB = _container.GetExportedValue<CommonInterface>();