在ninject框架中绑定时出现类型转换错误

Question

我是 Dependency Injection 的新手，并且使用推荐 ninjectKernel 作为 DI 框架的书，book 在这里被引用。我在以下方法中遇到错误：

 protected override IController GetControllerInstance(RequestContext requestContext, Type controllerType)
        {
            return controllerType == null
                ? null
                : (IController)ninjectKernel.Get(controllerType);
        }

它抛出

无法将“System.String”类型的对象转换为“SportsStore.Domain.Concrete.EmailSettings”类型。

在添加绑定（如下）之前，一切正常。

private void AddBindings() {

    ninjectKernel.Bind<IProductsRepository>().To<EFProductRepository>();

    EmailSettings emailSettngs = new EmailSettings {
        WriteAsFile = bool.Parse(ConfigurationManager
            .AppSettings["Email.WriteAsFile"] ?? "false")
    };

    ninjectKernel.Bind<IOrderProcessor>()
        .To<EmailOrderProcessor>()
        .WithConstructorArgument("settings", "emailSettings");
}

你能给我一些提示吗？

这是堆栈跟踪：

[InvalidCastException：无法将“System.String”类型的对象转换为“SportsStore.Domain.Concrete.EmailSettings”类型。] DynamicInjectorc4f1546a04fc4966a278bd8198a4edff(Object[]) +123 Ninject.Activation.Providers.StandardProvider.Create（IContext 上下文）+884 Ninject.Activation.Context.ResolveInternal（对象范围）+218 Ninject.Activation.Context.Resolve() +277 Ninject.c__DisplayClass15.b__f(IBinding 绑定) +86 System.Linq.WhereSelectEnumerableIterator2.MoveNext() +145 System.Linq.Enumerable.SingleOrDefault(IEnumerable1 来源）+4059897 Ninject.Planning.Targets.Target1.GetValue(Type service, IContext parent) +169 Ninject.Planning.Targets.Target1.ResolveWithin(IContext parent) +747 Ninject.Activation.Providers.StandardProvider.GetValue（IContext 上下文，ITarget 目标）+269 Ninject.Activation.Providers.c__DisplayClass4.b__2（ITarget 目标）+69 System.Linq.WhereSelectArrayIterator2.MoveNext() +66 System.Linq.Buffer1..ctor(IEnumerable1 source) +323 System.Linq.Enumerable.ToArray(IEnumerable1 源) +77 Ninject.Activation.Providers.StandardProvider.Create（IContext 上下文）+847 Ninject.Activation.Context.ResolveInternal（对象范围）+218 Ninject.Activation.Context.Resolve() +277 Ninject.c__DisplayClass15.b__f(IBinding 绑定) +86 System.Linq.WhereSelectEnumerableIterator2.MoveNext() +145 System.Linq.Enumerable.Single(IEnumerable1 来源）+191 Ninject.ResolutionExtensions.Get(IResolutionRoot root, Type service, IParameter[] parameters) +70 SportsStore.WebUI.Infrastructure.NinjectControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) 在 c:\dev\aspnet\Workout\SportsStore\SportsStore.WebUI\Infrastructure\NinjectControllerFactory.cs:26 System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +74 System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& 控制器, IControllerFactory& 工厂) +193 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback 回调, 对象状态) +49 System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback 回调, 对象状态) +49 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +16 System.Web.Mvc.c__DisplayClass7.b__6() +31 System.Web.Mvc.ServerExecuteHttpHandlerWrapper.Wrap(Func1 func) +27 System.Web.Mvc.ServerExecuteHttpHandlerAsyncWrapper.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +98 System.Web.HttpServerUtility.ExecuteInternal(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage, VirtualPath path, VirtualPath filePath, String physPath, Exception error, String queryStringOverride) +2019 System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm, Boolean setPreviousPage) +76 System.Web.HttpServerUtility.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +28 System.Web.HttpServerUtilityWrapper.Execute(IHttpHandler handler, TextWriter writer, Boolean preserveForm) +19 System.Web.Mvc.Html.ChildActionExtensions.ActionHelper(HtmlHelper htmlHelper, String actionName, String controllerName, RouteValueDictionary routeValues, TextWriter textWriter) +477 System.Web.Mvc.Html.ChildActionExtensions.RenderAction(HtmlHelper htmlHelper, String actionName, String controllerName) +34 ASP._Page_Views_Shared__Layout_cshtml.Execute() in c:\dev\aspnet\Workout\SportsStore\SportsStore.WebUI\Views\Shared\_Layout.cshtml:12 System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197 System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +96 System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +88 System.Web.WebPages.<>c__DisplayClass7.<RenderPageCore>b__6(TextWriter writer) +233 System.Web.WebPages.HelperResult.WriteTo(TextWriter writer) +10 System.Web.WebPages.WebPageBase.Write(HelperResult result) +71 System.Web.WebPages.WebPageBase.RenderSurrounding(String partialViewName, Action1 正文) +64 System.Web.WebPages.WebPageBase.PopContext() +246 System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +95 System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +259 System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +115 System.Web.Mvc.ViewResultBase.ExecuteResult（ControllerContext 上下文）+294 System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13 System.Web.Mvc.c__DisplayClass1a.b__17() +23 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter（IResultFilter 过滤器，ResultExecutingContext preContext，Func1 continuation) +242 System.Web.Mvc.<>c__DisplayClass1c.<InvokeActionResultWithFilters>b__19() +21 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList1 过滤器，ActionResult actionResult）+175 System.Web.Mvc.Async.c__DisplayClass2a.b__20() +89 System.Web.Mvc.Async.c__DisplayClass25.b__22(IAsyncResult asyncResult) +102 System.Web.Mvc.Async.WrappedAsyncResult1.End() +57 System.Web.Mvc.Async.AsyncControllerActionInvoker.EndInvokeAction(IAsyncResult asyncResult) +43 System.Web.Mvc.<>c__DisplayClass1d.<BeginExecuteCore>b__18(IAsyncResult asyncResult) +14 System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23 System.Web.Mvc.Async.WrappedAsyncResult1.End() +62 System.Web.Mvc.Controller.EndExecuteCore(IAsyncResult asyncResult) +57 System.Web.Mvc.Async.c__DisplayClass4.b__3(IAsyncResult ar) +23 System.Web.Mvc.Async.WrappedAsyncResult1.End() +62 System.Web.Mvc.Controller.EndExecute(IAsyncResult asyncResult) +47 System.Web.Mvc.Controller.System.Web.Mvc.Async.IAsyncController.EndExecute(IAsyncResult asyncResult) +10 System.Web.Mvc.<>c__DisplayClass8.<BeginProcessRequest>b__3(IAsyncResult asyncResult) +25 System.Web.Mvc.Async.<>c__DisplayClass4.<MakeVoidDelegate>b__3(IAsyncResult ar) +23 System.Web.Mvc.Async.WrappedAsyncResult1.End() +62 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +47 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult 结果) +9 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9690172 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +155

Answer 1

您将字符串而不是emailSettings 对象传递给构造函数参数。取消字符串emailSettings。

ninjectKernel.Bind<IOrderProcessor>()
    .To<EmailOrderProcessor>()
    .WithConstructorArgument("settings", emailSettings);