Question

I have a view model class which uses UnitOfWork to some database operations like fetching of items to create select lists and IPrincipal for some auditing (like modified by etc.). It cannot work without this UOW. I have configured my web site to use Ninject to inject UOW into Controllers. From controller I pass this UOW when creating view model. But when performing POST operation I am getting

No parameterless constructor defined for this object. 

I have few SelectList type of properties which I have excluded with Bind attribute.

How can I overcome this problem? Can I configure Ninject to create the objects of this type and make ModelBinder use it?

Answer 1

Perhaps inheriting from DefaultModelBinder and resolving the model classes via Ninject?

Update:

NinjectModelBinder.cs

public class NinjectModelBinder : DefaultModelBinder
{
    private readonly StandardKernel _kernel;

    public NinjectModelBinder(StandardKernel kernel)
    {
        _kernel = kernel;
    }

    protected override object CreateModel(ControllerContext controllerContext, 
                              ModelBindingContext bindingContext, Type modelType)
    {
        var model = _kernel.TryGet(modelType);
        if (model != null) return model;
        return base.CreateModel(controllerContext, bindingContext, modelType);
    }
}

Global.asax.cs

public class MvcApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();

        WebApiConfig.Register(GlobalConfiguration.Configuration);
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);

        var kernel = new StandardKernel();
        ModelBinders.Binders.DefaultBinder = new NinjectModelBinder(kernel);
    }
}