没有为此对象定义 MVC 控制器的无参数构造函数

Question

如您所见，我有这个控制器：

namespace Web.Front.Controllers
{
    public class CarController : Controller
    {
        ICarService _CarService;
        public  CarController(ICarService carService)
        {
            _CarService = carService;
        }

        // GET: Car

        public ActionResult Index()
        {

            return View();
        }
    }
}

当我调用索引操作时出现此错误：

 No parameterless constructor defined for this object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.MissingMethodException: No parameterless constructor defined for this object.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:


[MissingMethodException: No parameterless constructor defined for this object.]
   System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck) +0
   System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark) +119
   System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark) +232
   System.Activator.CreateInstance(Type type, Boolean nonPublic) +83
   System.Activator.CreateInstance(Type type) +11
   System.Web.Mvc.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType) +55

[InvalidOperationException: An error occurred when trying to create a controller of type 'Web.Front.Controllers.CarController'. Make sure that the controller has a parameterless public constructor.]
   System.Web.Mvc.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType) +178
   System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) +80
   System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +102
   System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +184
   System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +50
   System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state) +48
   System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData) +16
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +103
   System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step) +48
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +159

请注意，我正在使用 ninject 向控制器注入服务。当我从构造函数中删除服务时，它会起作用。

ninject代码：

  private static void RegisterServices(IKernel kernel)
    {
        kernel.Bind<DidbaanContext>().To<DidbaanContext>();
        kernel.Bind<ICarService>().To<CarService>();
        kernel.Bind<ICarRepository>().To<CarRepository>();

    }

Answer 1

mvc 需要无参数结构。如果您没有构造函数，.Net-runtime 会自动创建无参数构造，否则如果您有带参数的构造，则运行时不会这样做并引发错误。

你在每个控制器上创建一个新的 carService，或者你使用一个 serviceProvider。单元测试对于服务提供商来说很简单。使用 asp.net 核心很容易 enter link description here, if you use mvc 4 or 5. you can see here a see here a sample enter link description here

没有为此对象定义 MVC 控制器的无参数构造函数

No parameterless constructor defined for this object for MVC Controller

model-view-controller

asp.net-mvc

constructor

ninject