MVC 4的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
下面是跟踪：
<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>
我觉得这是不可思议的公共类UsersController：ApiController {...} 工作就好了。我比较了2个控制器，所有的设置和结构是相似的。
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.
我使用 Ninject 和我有我类似杰米·库尔茨 <系统设置href=\"http://www.amazon.ca/gp/product/1430249773/ref=s9_simh_gw_p14_d11_i1?pf_rd_m=A3DWYIK6Y9EEQB&pf_rd_s=center-4&pf_rd_r=18BS0P23TZH1Q8KWS8JK&pf_rd_t=101&pf_rd_p=1375923642&pf_rd_i=915398\">Asp.Net MVC 4和Web API：从开始建立一个REST服务来完成
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，是任何人都能够发现的问题，以及如何解决呢？谢谢！
From the stack trace, is anyone able to spot the problem and how to solve it? Thanks!
的要求。的
As Requested.
ContinentsController
[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 ：工作得很好。
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);
}
}
我使用 NinjectWebCommon.cs ，并在其中，我有这个和其他一些默认方式：
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>();
.........
}
.......
}
两者 NinjectWebCommon.cs 和 NinjectConfigurator.cs 位于 App_Start 文件夹中。
container.Bind＆LT; ISession的方式＆gt;（）ToMethod（了createSession）; 是 NHibernate的。它是在 NinjectConfigurator.cs 在私人无效ConfigureNHibernate（容器的iKernel）{...}
推荐答案
此错误是一个已知的错误，当你没有设置在您的应用程序依赖解析器。控制器工厂找不到参数的构造函数来创建控制器和执行动作的方法（或动词的方法？）。所以，你必须创建一个依赖解析器类并将它放在你的web应用程序的初始化。这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：
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());
}
}
}
的 NinjectDependencyResolver 类需要一个 Ninject StandardKernel 对象作为构造函数的参数，并使用该参考每当一个依赖范围是流水线。
为了使这一切工作，在 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;
}
在在Application_Start事件后，你的的Global.asax.cs 文件，调用这个 CreateKernel 方法。
On your Global.asax.cs file in the end of Application_Start event, call this CreateKernel method.
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