Prism / MEF -- Once my app is running, how do I add to my AggregateCatalog later on?

Basically, I have the following scenario:

1. User runs application
2. The Bootstrapper loads the "Modules" directory into the AggregateCatalog.
3. My navigation menu is built
4. The user clicks refresh
5. The app downloads a new module and copies it into the Module directory.

I somehow need to be able to add in the new module to my AggregateCatal开发者_运维百科og and update my navigation menu. I figure a "AllowRecomposition" is necessary, but how do I actually add the new assembly to my AggregateCatalog after my app is already running?

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If you import the AggregateCatalog you can access it from within your ViewModel (or wherever else you want to add to it.

[Import()]
private AggregateCatalog _aggregateCatalog;

...

private void SomeFunc()
{
    _aggregateCatalog.Catalogs.Add(...);
}

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NOTE: If the Assembly would affect any Import or ImportMany statements, they must allow for recomposition or you will get an exception. For example, if your assembly contains another IFooService export...

//Exception Thrown
[ImportMany(typeof(IFooService))]
private IEnumerable<IFooService> _myFooServices;

//No Exception Thrown
[ImportMany(typeof(IFooService), AllowRecomposition = true)]
private IEnumerable<IFooService> _myFooServices;

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NOTE: You will trigger OnImportsSatisfied if you implemented the IPartImportsSatisfiedNotification interface again, so ensure that your application does not have issues because of this.