WPF - MVVM multiple projects structure

Question

I always developed application in MVVM in one project and separate Model, View, ViewModel wth folders. Looking in different questions and different books I learnt that separate them in different projects will be better for different reasons so I was trying to develop a simple project to see how it works.

Firstly I created a single project with different folders, and i start the application and it works good. This how is the structured the "single project" I have omitted the Model folder.

After I created multiple project composed of these 3 projects:

-MVVM

-MVVM.Views

-MVVM.ViewModels

This how i structured the "multiple project"

I set the MVVM.Views,MVVM.ViewModels output type to Dll and not to .exe, i added the projects(MVVM.Views,MVVM.ViewModels) references in MVVM.

But when i lunch the application i get an error

An unhandled exception of type 'System.Exception' occurred in WindowsBase.dll Informations: Could not locate any instances of contract MVVM.ViewModels.IShell.

I'm using also Caliburn.Micro 2.0.2 for bootstrapp and this is the MefBootstrapper:

public class MefBootstrapper : BootstrapperBase
{
    private CompositionContainer container;

    public MefBootstrapper()
    {
        Initialize();
    }

    protected override void Configure()
    {
        var catalog = new AggregateCatalog(
                AssemblySource.Instance.Select(x => new AssemblyCatalog(x)).OfType<ComposablePartCatalog>()
                );

        container = new CompositionContainer(catalog);

        var batch = new CompositionBatch();

        batch.AddExportedValue<IWindowManager>(new WindowManager());
        batch.AddExportedValue<IEventAggregator>(new EventAggregator());
        batch.AddExportedValue(container);

        container.Compose(batch);


        }

        protected override object GetInstance(Type serviceType, string key)
        {
            string contract = string.IsNullOrEmpty(key) ? AttributedModelServices.GetContractName(serviceType) : key;
            var exports = container.GetExportedValues<object>(contract);

            if (exports.Count() > 0)
                return exports.First();

            throw new Exception(string.Format("Could not locate any instances of contract {0}.", contract));
        }

        protected override IEnumerable<object> GetAllInstances(Type serviceType)
        {
            return container.GetExportedValues<object>(AttributedModelServices.GetContractName(serviceType));
        }

        protected override void BuildUp(object instance)
        {
            container.SatisfyImportsOnce(instance);
        }

        protected override void OnStartup(object sender, StartupEventArgs e)
        {
            DisplayRootViewFor<IShell>();
        }
    }

This is ViewModel code:

namespace MVVM.ViewModels
{
    public interface IShell { }

    [Export(typeof(IShell))]
    public class MainViewModel : PropertyChangedBase, IShell
    {

    }
}

I want to understand where i wrong? I missed one step? Thanks for support

Answer 1

I post the answer just in case someone will have my same problems. After reading a lot of posts and different stuff I've found the error. I forgot to load the assemblies into the application. And this is really easy just change the Configure() void here the code:

protected override void Configure()
{
    string pluginPath = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "");
    if (!Directory.Exists(pluginPath))
        Directory.CreateDirectory(pluginPath);

    var fi = new DirectoryInfo(pluginPath).GetFiles("*.dll");
    AssemblySource.Instance.AddRange(fi.Select(fileInfo => Assembly.LoadFrom(fileInfo.FullName)));

    var catalog = new AggregateCatalog(
            AssemblySource.Instance.Select(x => new AssemblyCatalog(x)).OfType<ComposablePartCatalog>()
            );

    container = new CompositionContainer(catalog);

    var batch = new CompositionBatch();

    batch.AddExportedValue<IWindowManager>(new WindowManager());
    batch.AddExportedValue<IEventAggregator>(new EventAggregator());
    batch.AddExportedValue(container);

    container.Compose(batch);
}