Question

我创建了一个自定义Action Filter并将其与Ninject的BindFilter方法绑定：

public class ExtendModelAttribute : FilterAttribute {}

public class ExtendModelFilter : IActionFilter
{
    private IKernel kernel;
    public ExtendModelFilter(Func<IKernel> kernel)
    {
        this.kernel = kernel;
    }

    public void OnActionExecuted(ActionExecutedContext filterContext)
    {
        // TODO:
    }

    public void OnActionExecuting(ActionExecutingContext filterContext)
    {
    }
}

我像这样绑定我的过滤器：

 kernel.BindFilter<ExtendModelFilter>(FilterScope.Action, 0).WhenActionMethodHas<ExtendModelAttribute>();

到目前为止，一切都很好。我想要完成的是：

[ExtendModel]
public ActionResult Index()
{
    return View(new IndexModel());
}

我希望ExtendModel过滤器做的是确定使用什么类型的Model，然后找到正确的依赖项：

public interface IModelExtender<TModel> {
    void Extend(TModel model);
}

public class IndexModelExtender : IModelExtender<IndexModel> {
    public void Extend(IndexModel model)
    {
        // extend the model here with anything extra that is required
    }
}

我不确定如何在动作过滤器中编写代码来获取IModelExtender的实例：

public void OnActionExecuted(ActionExecutedContext filterContext)
{
    // TODO:
    // I Need to look at the filterContext Model to determine which 
    // type of IModelExtender<T> to create:
    // For Example, when [ExtendModel] is applied on the Index() method above
    // then I need it to resolve to IndexModelExtender
}

也许我想要做的甚至不可能？由于我在编译时不知道T是什么，有什么办法可以做我想要的吗？

修改
以下是ModelExtender可能执行的操作的示例：

public class IndexModelExtender : IModelExtender<IndexModel>
{
    public IndexModelExtender(IFooRepository fooRepository, IBarRepository barRepository)
     {
        // ...
     }

     public void Extend(IndexModel model)
     {
         model.SelectList1 = new SelectList(fooRepository.GetFoos(), "Description", "Id");
         model.SelectList2 = new SelectList(barRepository.GetBars(), "Description", "Id");
     }
}

我想在我的控制器中避免这样的代码：

 public ActionResult Index()
 {
     var model = new IndexModel();
     // populate select lists here
     return View(model);
 }

 [HttpPost]
 public ActionResult Index(IndexModel model)
 {
     if(!ModelState.IsValid ) {
        // populate the same stuff here
     }
  }

Answer 1

您必须使用反射，因为模型类型仅在运行时已知并且您的扩展器是通用的：

public class ExtendModelFilter : IActionFilter
{
    public void OnActionExecuted(ActionExecutedContext filterContext)
    {
        object model = null;
        if (filterContext.Result is ViewResultBase)
        {
            model = ((ViewResultBase)filterContext.Result).Model;
        }
        else if (filterContext.Result is JsonResult)
        {
            model = ((JsonResult)filterContext.Result).Data;
        }
        // TODO: you could continue with the else if here to take
        // into account some other action results that have the notion of model
        // like for example some custom action results that you might have written

        if (model == null)
        {
            // we have no model => nothing to extend
            return;
        }

        var extenderType = typeof(IModelExtender<>).MakeGenericType(model.GetType());
        var extender = DependencyResolver.Current.GetService(extenderType);
        var extend = extenderType.GetMethod("Extend");
        extend.Invoke(extender, new[] { model });
    }

    public void OnActionExecuting(ActionExecutingContext filterContext)
    {
    }
}

您还会注意到我已经重构了自定义操作过滤器，以便使用当前依赖项解析程序并使其与NInject无关。如果您愿意，您当然可以保留IKernel依赖关系。

Ninject在动作过滤器中

1 个答案: