MEF: DirectoryPartCatalog

Question

I'm trying to write a simple MEF demo to learn about it. I'm following this tutorial, but it seems to be outdated. The downloadable example works, but it uses an included assembly that is 2 versions older (2008.9.4.0) than the current one (4.0) that ships with Framwework 4.

In particular, it uses DirectoryPartCatalog that I cannot find anywhere in the newest library. Could anyone provide an example on how to discover pluggable assemblies from a directory with the current version of MEF?

Thanks

Answer 1

You need to make several changes to make this sample compile and run with builtin version of System.ComponentModel.Composition.

class Program
{
    [ImportMany] // [Import]
    public IEnumerable<string> Messages { get; set; }

    [ImportMany] // [Import]
    public IEnumerable<IOutputString> OutputSet { get; set; }

    [Import("OutputMessages")]
    public Action<IEnumerable<IOutputString>, IEnumerable<string>> OutputMessages { get; set; }

    public void Run()
    {

        var catalog = new AggregateCatalog(); // AggregatingComposablePartCatalog
        catalog.Catalogs.Add(new DirectoryCatalog(@"..\..\..\ExternalMessages\bin\Debug")); // DirectoryPartCatalog
        catalog.Catalogs.Add(new DirectoryCatalog(@"..\..\..\ExtraMessages")); // DirectoryPartCatalog
        catalog.Catalogs.Add(new AssemblyCatalog(Assembly.GetExecutingAssembly())); // AttributedAssemblyPartCatalog
        var container = new CompositionContainer(catalog); // CompositionContainer(catalog.CreateResolver());

        // container.AddPart(this);
        // container.Compose();
        container.ComposeParts(this);

        OutputMessages(OutputSet, Messages);

    }

    static void Main(string[] args)
    {
        Program p = new Program();
        p.Run();
    }
}