MVC 4 Web Api 控制器没有默认构造函数? [英] MVC 4 Web Api Controller does not have a default constructor?
问题描述
这是跟踪:
<Error>
<Message>An error has occurred.</Message>
<ExceptionMessage>
Type 'ProjectName.Web.Api.Controllers.ContinentsController' does not have a default constructor
</ExceptionMessage>
<ExceptionType>System.ArgumentException</ExceptionType>
<StackTrace>
at System.Linq.Expressions.Expression.New(Type type)
at System.Web.Http.Internal.TypeActivator.Create[TBase](Type instanceType)
at System.Web.Http.Dispatcher.DefaultHttpControllerActivator.GetInstanceOrActivator(HttpRequestMessage request, Type controllerType, Func`1& activator)
at System.Web.Http.Dispatcher.DefaultHttpControllerActivator.Create(HttpRequestMessage request, HttpControllerDescriptor controllerDescriptor, Type controllerType)
</StackTrace>
</Error>
我觉得这很奇怪，因为 public class UsersController : ApiController { ... } 工作得很好.我比较了2个控制器，所有的设置和结构都相似.
I find this weird as public class UsersController : ApiController { ... } is working just fine. I have compared the 2 controllers, all the settings and structures are similar.
我正在使用 Ninject 并且我的系统设置类似于 Jamie Kurtz Asp.Net的mvc 4和网络API:大厦有REST 服务从头到尾.
I am using Ninject and i have my system setup similar to Jamie Kurtz Asp.Net Mvc 4 and the Web Api: Building a REST Service from Start to Finish.
从堆栈跟踪中，是否有人能够发现问题以及如何解决?谢谢！
From the stack trace, is anyone able to spot the problem and how to solve it? Thanks!
根据要求.
大陆控制器
[LoggingNHibernateSession]
public class ContinentsController : ApiController
{
private readonly ISession _session;
private readonly IContinentMapper _continentMapper;
private readonly IHttpContinentFetcher _httpContinentFetcher;
private readonly IDateTime _dateTime;
public ContinentsController(ISession session, IContinentMapper continentMapper, IHttpContinentFetcher continentFetcher, IDateTime dateTime)
{
_session = session;
_continentMapper = continentMapper;
_httpContinentFetcher = continentFetcher;
_dateTime = dateTime;
}
public IEnumerable<Continent> Get()
{
var continents = _session
.Query<Data.Model.Continent>()
.Select(_continentMapper.CreateContinent)
.ToList();
return continents;
}
public Continent Get(long id)
{
var modelContinent = _httpContinentFetcher.GetContinent(id);
var continent = _continentMapper.CreateContinent(modelContinent);
return continent;
}
}
UsersController:工作正常.
public class UsersController : ApiController
{
private readonly ISession _session;
private readonly IUserManager _userManager;
private readonly IUserMapper _userMapper;
private readonly IHttpUserFetcher _userFetcher;
public UsersController(
IUserManager userManager,
IUserMapper userMapper,
IHttpUserFetcher userFetcher,
ISession session)
{
_userManager = userManager;
_userMapper = userMapper;
_userFetcher = userFetcher;
_session = session;
}
[Queryable]
public IQueryable<Data.Model.User> Get()
{
return _session.Query<Data.Model.User>();
}
[LoggingNHibernateSession]
public User Get(Guid id)
{
var user = _userFetcher.GetUser(id);
return _userMapper.CreateUser(user);
}
}
我正在使用 NinjectWebCommon.cs 并且在其中，我有这个和其他一些默认方法.:
I am using NinjectWebCommon.cs and in it, i have this and a few other default methods.:
private static void RegisterServices(IKernel kernel)
{
var containerConfigurator = new NinjectConfigurator();
containerConfigurator.Configure(kernel);
GlobalConfiguration.Configuration.MessageHandlers.Add(kernel.Get<BasicAuthenticationMessageHandler>());
}
然后我有 NinjectConfigurator.cs:
public class NinjectConfigurator
{
......
private void AddBindings(IKernel container)
{
.....
container.Bind<IDateTime>().To<DateTimeAdapter>();
container.Bind<IDatabaseValueParser>().To<DatabaseValueParser>();
//HttpFetchers
container.Bind<IHttpUserFetcher>().To<HttpUserFetcher>();
container.Bind<IHttpContinentFetcher>().To<HttpContinentFetcher>();
//TypeMappers
container.Bind<IUserManager>().To<UserManager>();
container.Bind<IMembershipInfoProvider>().To<MembershipAdapter>();
container.Bind<IUserMapper>().To<UserMapper>();
container.Bind<IContinentMapper>().To<ContinentMapper>();
.........
}
.......
}
NinjectWebCommon.cs 和 NinjectConfigurator.cs 都位于 App_Start 文件夹中.
Both NinjectWebCommon.cs and NinjectConfigurator.cs are located in the App_Start folder.
container.Bind 是 NHibernate.它在 NinjectConfigurator.cs 内 private void ConfigureNHibernate(IKernel container) { ... }
推荐答案
当您未在应用程序中设置依赖项解析器时，此错误是一个已知错误.控制器工厂找不到无参数构造函数来创建控制器并执行操作方法(或动词方法?).因此，您必须创建一个依赖解析器类并在您的 Web 应用程序的初始化时设置它.它将解决您的控制器的依赖关系.
This error is a known error when you do not set the dependency resolver in your application. The Controller Factory could not find a parameterless constructor to create the controller and execute the action method (or verb method?). So, you have to create a dependency resolver class and set it on the initialization of your web app. It will resolve dependencies of your controllers.
使用 ninject，你可以尝试这样的事情:
Using ninject, you could try something like this:
using Ninject;
using Ninject.Syntax;
using System;
using System.Collections.Generic;
using System.Diagnostics.Contracts;
using System.Web.Http.Dependencies;
namespace MyApplication.App_Start
{
public class NinjectDependencyScope : IDependencyScope
{
private IResolutionRoot resolver;
internal NinjectDependencyScope(IResolutionRoot resolver)
{
Contract.Assert(resolver != null);
this.resolver = resolver;
}
public void Dispose()
{
IDisposable disposable = resolver as IDisposable;
if (disposable != null)
disposable.Dispose();
resolver = null;
}
public object GetService(Type serviceType)
{
if (resolver == null)
throw new ObjectDisposedException("this", "This scope has already been disposed");
return resolver.TryGet(serviceType);
}
public IEnumerable GetServices(Type serviceType)
{
if (resolver == null)
throw new ObjectDisposedException("this", "This scope has already been disposed");
return resolver.GetAll(serviceType);
}
}
public class NinjectDependencyResolver : NinjectDependencyScope, IDependencyResolver
{
private IKernel kernel;
public NinjectDependencyResolver(IKernel kernel)
: base(kernel)
{
this.kernel = kernel;
}
public IDependencyScope BeginScope()
{
return new NinjectDependencyScope(kernel.BeginBlock());
}
}
}
NinjectDependencyResolver 类接受一个 Ninject StandardKernel 对象作为构造函数参数，只要依赖范围被流水线化，就会使用这个引用.为了使这一切工作，NinjectDependencyResolver 类被分配给应用程序的全局配置:
The NinjectDependencyResolver class takes a Ninject StandardKernel object as a constructor argument and this reference is used whenever a dependency scope is pipelined.
To make this all work, the NinjectDependencyResolver class is assigned to the application's global configuration:
private static IKernel CreateKernel()
{
var kernel = new StandardKernel();
kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel);
kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>();
// register all your dependencies on the kernel container
RegisterServices(kernel);
// register the dependency resolver passing the kernel container
GlobalConfiguration.Configuration.DependencyResolver = new NinjectDependencyResolver(kernel);
return kernel;
}
在 Application_Start 事件末尾的 Global.asax.cs 文件中，调用此 CreateKernel 方法.
On your Global.asax.cs file in the end of Application_Start event, call this CreateKernel method.
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