SignalR, MEF and Dependency Injection working together

Question

I'm trying to get SignalR, MEF, and MVC working together.

Here is my resolver class:

public class SignalRDependencyResolver : DefaultDependencyResolver
{
    private readonly CompositionContainer _container;

    public SignalRDependencyResolver(CompositionContainer container)
    {
        _container = container;
    }

    public override object GetService(Type serviceType)
    {
        if (serviceType == null)
        {
            throw new ArgumentNullException("serviceType");
        }

        var name = AttributedModelServices.GetContractName(serviceType);
        var export = _container.GetExportedValueOrDefault<object>(name);
        return export;
    }

    public override IEnumerable<object> GetServices(Type serviceType)
    {
        if (serviceType == null)
        {
            throw new ArgumentNullException("serviceType");
        }

        var exports = _container.GetExportedValues<object>(AttributedModelServices.GetContractName(serviceType));
        return exports;
    }
}

And here is my Owin startup:

public class Startup
{
    public void Configuration(IAppBuilder app)
    {
        var resolver = new SignalRDependencyResolver(MefConfigWeb.Container);
        var config = new HubConfiguration
        {
            Resolver = resolver,
        };

        app.MapSignalR(config);
    }
}

I can break on Startup class and see that the container does include my exports. However, Visual Studio prompts with an exception:

Unhandled exception at line 244, column 13 in http://localhost:3928/Scripts/jquery.signalR-2.0.0.js

0x800a139e - JavaScript runtime error: SignalR: Error loading hubs. Ensure your hubs reference is correct, e.g. .

The app works fine if I don't set my custom dependency resolver and New up my dependency inside the Hub class.

I am following along from this tutorial: http://www.asp.net/signalr/overview/signalr-20/extensibility/dependency-injection

Any ideas why this is not working?

davidfowl davidfowl · Accepted Answer · 2013-10-27T06:22:26

2

votes

You need to call the base implementation when you don't have the service.

SignalR, MEF and Dependency Injection working together

1 Answers