MVC 4 Web Api控制器没有默认构造函数？

Question

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,public class UsersController : ApiController { ... }工作得很好.我比较了2个控制器,所有设置和结构都相似.

我正在使用Ninject我的系统设置类似于Jamie Kurtz Asp.Net Mvc 4和Web Api:从开始到完成构建REST服务.

从堆栈跟踪,是否有人能够发现问题以及如何解决它？谢谢!

按照要求.

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);
        }
    }

我正在使用NinjectWebCommon.cs它,我有这个和其他一些默认方法:

        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>();    
            .........
        }
     .......
}

这两个NinjectWebCommon.cs和NinjectConfigurator.cs位于在App_Start文件夹中.

container.Bind<ISession>().ToMethod(CreateSession);是NHibernate.它在NinjectConfigurator.cs里面private void ConfigureNHibernate(IKernel container) { ... }

Answer 1

如果未在应用程序中设置依赖项解析程序,则此错误是已知错误.Controller Factory找不到无参数构造函数来创建控制器并执行action方法(或动词方法？).因此,您必须创建依赖项解析程序类并将其设置为Web应用程序的初始化.它将解决控制器的依赖关系.

使用ninject,您可以尝试这样的事情:

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());         
        }     
    } 
}

所述NinjectDependencyResolver类需要一个Ninject StandardKernel对象作为构造器参数,每当一个依赖范围流水线使用此参考.为了使这一切工作,NinjectDependencyResolver该类被分配给应用程序的全局配置:

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Global.asax.csApplication_Start事件结束时的文件中,调用此CreateKernel方法.

Answer 2

您需要告诉Ninject如何正确解析Web API依赖项.

您可以使用Felipe Oriani的答案,但如果您愿意,可以使用名为WebApiContrib.IoC.Ninject的NuGet包,它将为您执行此操作.

1. 在Visual Studio中转到:工具> NuGet包管理器>管理解决方案的NuGet包

2. 安装WebApiContrib.IoC.Ninject包

3. 编辑:NinjectWebCommon.cs并更新CreateKernel()方法以包含:GlobalConfiguration.Configuration.DependencyResolver = new NinjectResolver(kernel);

   private static IKernel CreateKernel()
   {
       var kernel = new StandardKernel();
   
       try
       {
           kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel);
           kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>();
   
           RegisterServices(kernel);
   
           //Note: Add the line below:
           GlobalConfiguration.Configuration.DependencyResolver = new NinjectResolver(kernel);
   
           return kernel;
       }
       catch
       {
           kernel.Dispose();
           throw;
       }
   }
   

Answer 3

对我来说，只需添加 Ninject.Web.WebApi.Webhost NuGet 包即可。

对于同时使用 MVC 和 WebApi2 的应用程序，我有以下 Ninject 包：

• 忍者
• Ninject.MVC5
• Ninject.Web.Common
• Ninject.Web.Common.WebHost
• Ninject.Web.WebApi
• Ninject.Web.WebApi.WebHost