在webapi actionfilter中使用ninject的正确方法

Question

I have been given a webapi2 application to manage and I've started to write some unit tests for it as it didn't have any.

Testing controllers and services are both pretty easy to do as they are injecting their dependencies via constructor injection.

For the actionfilters I see things are done differently as its not possible to use constructor injection.

Now I haven't really used ninject much before but this an example of how the filters have been setup.

public class CustomFilterAttribute : ActionFilterAttribute
{
    public ILog Log { get; set; }

    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        var id = int.Parse(actionContext.ActionArguments["id"].ToString());
        Log = actionContext.Request
            .GetDependencyScope()
            .GetService(typeof(ILog))
            as ILog;


     Log.WriteMessage(string.Format("Got id:{0}",id));

   }
}

My registration looks like

kernel.Bind<ILog>().ToConstant(new Log());

Does this look ok? I am not sure how to write a test for the filter, do I somehow need to mock the .GetDependencyScope to include my required ILog ?

The way Log is getting wired up within the filter is this right?

Answer 1

In order to access it via the DependencyResolver you need to register it with the http configuration.

public class NinjectDependencyResolver : NinjectDependencyScope, IDependencyResolver, System.Web.Mvc.IDependencyResolver {
   private readonly IKernel kernel;

   public NinjectDependencyResolver(IKernel kernel)
       : base(kernel) {
       this.kernel = kernel;
   }

   public IDependencyScope BeginScope() {
       return new NinjectDependencyScope(this.kernel.BeginBlock());
   }
}

And then register it during startup...

// Use the kernal and the NinjectDependencyResolver as
// application's resolver
var resolver = new NinjectDependencyResolver(kernal);

//Register Resolver for Web Api
GlobalConfiguration.Configuration.DependencyResolver = resolver;

You can access the resolver via the ActionContext

public class CustomFilterAttribute : ActionFilterAttribute {
    public ILog Log { get; set; }

    public override void OnActionExecuting(HttpActionContext actionContext) {
        var id = int.Parse(actionContext.ActionArguments["id"].ToString());
        Log = actionContext
            .RequestContext
            .Configuration
            .DependencyResolver
            .GetService(typeof(ILog))
            as ILog;


       Log.WriteMessage(string.Format("Got id:{0}",id));
   }
}