I have a Silverlight 4 library L which has a dependency that is to be provided at run-time via a plugin P.
I am using a DeploymentCatalog along the lines of the example provided by MEF documentation and all is well: the XAP of the plugin P is correctly downloaded asynchronously and the import is satisfied.
However, I cannot control the details on the Silverlight application A that will be using library L and I cannot exclude that A itself might want to use MEF: therefore it's possible that at some point A might issue a CompositionHost.SatisfyImports(...)CompositionHost.Initialize(catalog) call for its own purposes which I understand can only be invoked once.
Am I missing something here or partitioning the application across multiple XAPs can only be achieved if one has complete control of the Silverlight application and libraries?
Stefano
CompositionHost.SatisfyImports can be called many times. CompositionHost.Initialize can only be called once. As a library, it is not a good idea to call that method because the application may do so. Since you need to create and use a DeploymentCatalog, it's probably better if you don't use CompositionHost at all in your library, since you want to avoid calling the Initialize method, which would be the way to hook the CompositionHost to the DeploymentCatalog.
You can create your own CompositionContainer hooked up to the DeploymentCatalog and call GetExports or SatisfyImports on the container you created. CompositionHost is pretty much just a wrapper around a static CompositionContainer.