我正在使用Ninject MVC3（版本3.0.0.0）为我的ASP.Net MVC3应用程序安装使用NuGet Package进行依赖注入。
以下是Global.asax更改：
public class MvcApplication : NinjectHttpApplication
{
public static void RegisterGlobalFilters(GlobalFilterCollection filters)
{
filters.Add(new HandleErrorAttribute());
}
public static void RegisterRoutes(RouteCollection routes)
{
routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
routes.IgnoreRoute("favicon.ico");
routes.IgnoreRoute("{*favicon}", new { favicon = @"(.*/)?favicon.ico(/.*)?" });
routes.MapRoute(
"Default", // Route name
"{controller}/{action}/{id}", // URL with parameters
new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults
);
}
protected override IKernel CreateKernel()
{
var kernel = new StandardKernel();
kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel);
kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>();
RegisterServices(kernel);
return kernel;
}
protected override void OnApplicationStarted()
{
base.OnApplicationStarted();
AreaRegistration.RegisterAllAreas();
RegisterGlobalFilters(GlobalFilters.Filters);
RegisterRoutes(RouteTable.Routes);
}
/// <summary>
/// Load your modules or register your services here!
/// </summary>
/// <param name="kernel">The kernel.</param>
private static void RegisterServices(IKernel kernel)
{
kernel.Bind<IUserRepository>().To<UserRepository>();
kernel.Bind<IUserService>().To<UserService>();
kernel.Bind<ICommonRepository>().To<CommonRepository>();
kernel.Bind<ICommonService>().To<CommonService>();
}
}
但它给出了以下错误，虽然我有我的HomeController的无参数构造函数：
System.NullReferenceException: Object reference not set to an instance of an object.
Generated: Wed, 28 Mar 2012 05:49:01 GMT
System.InvalidOperationException: An error occurred when trying to create a controller of type 'MVC3.Web.Controllers.HomeController'. Make sure that the controller has a parameterless public constructor. ---> System.NullReferenceException: Object reference not set to an instance of an object.
at Ninject.Planning.Bindings.BindingConfiguration.GetProvider(IContext context) in c:\Projects\Ninject\ninject\src\Ninject\Planning\Bindings\BindingConfiguration.cs:line 107
at Ninject.Planning.Bindings.Binding.GetProvider(IContext context) in c:\Projects\Ninject\ninject\src\Ninject\Planning\Bindings\Binding.cs:line 212
at Ninject.Activation.Context.Resolve() in c:\Projects\Ninject\ninject\src\Ninject\Activation\Context.cs:line 157
at Ninject.KernelBase.<>c__DisplayClass10.<Resolve>b__c(IBinding binding) in c:\Projects\Ninject\ninject\src\Ninject\KernelBase.cs:line 386
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
at Ninject.Planning.Targets.Target`1.GetValue(Type service, IContext parent) in c:\Projects\Ninject\ninject\src\Ninject\Planning\Targets\Target.cs:line 197
at Ninject.Planning.Targets.Target`1.ResolveWithin(IContext parent) in c:\Projects\Ninject\ninject\src\Ninject\Planning\Targets\Target.cs:line 165
at Ninject.Activation.Providers.StandardProvider.GetValue(IContext context, ITarget target) in c:\Projects\Ninject\ninject\src\Ninject\Activation\Providers\StandardProvider.cs:line 114
at Ninject.Activation.Providers.StandardProvider.<>c__DisplayClass4.<Create>b__2(ITarget target) in c:\Projects\Ninject\ninject\src\Ninject\Activation\Providers\StandardProvider.cs:line 96
at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
at Ninject.Activation.Providers.StandardProvider.Create(IContext context) in c:\Projects\Ninject\ninject\src\Ninject\Activation\Providers\StandardProvider.cs:line 96
at Ninject.Activation.Context.Resolve() in c:\Projects\Ninject\ninject\src\Ninject\Activation\Context.cs:line 157
at Ninject.KernelBase.<>c__DisplayClass10.<Resolve>b__c(IBinding binding) in c:\Projects\Ninject\ninject\src\Ninject\KernelBase.cs:line 386
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
at Ninject.Planning.Targets.Target`1.GetValue(Type service, IContext parent) in c:\Projects\Ninject\ninject\src\Ninject\Planning\Targets\Target.cs:line 197
at Ninject.Planning.Targets.Target`1.ResolveWithin(IContext parent) in c:\Projects\Ninject\ninject\src\Ninject\Planning\Targets\Target.cs:line 165
at Ninject.Activation.Providers.StandardProvider.GetValue(IContext context, ITarget target) in c:\Projects\Ninject\ninject\src\Ninject\Activation\Providers\StandardProvider.cs:line 114
at Ninject.Activation.Providers.StandardProvider.<>c__DisplayClass4.<Create>b__2(ITarget target) in c:\Projects\Ninject\ninject\src\Ninject\Activation\Providers\StandardProvider.cs:line 96
at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
at Ninject.Activation.Providers.StandardProvider.Create(IContext context) in c:\Projects\Ninject\ninject\src\Ninject\Activation\Providers\StandardProvider.cs:line 96
at Ninject.Activation.Context.Resolve() in c:\Projects\Ninject\ninject\src\Ninject\Activation\Context.cs:line 157
at Ninject.KernelBase.<>c__DisplayClass10.<Resolve>b__c(IBinding binding) in c:\Projects\Ninject\ninject\src\Ninject\KernelBase.cs:line 386
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
at Ninject.Planning.Targets.Target`1.GetValue(Type service, IContext parent) in c:\Projects\Ninject\ninject\src\Ninject\Planning\Targets\Target.cs:line 197
at Ninject.Planning.Targets.Target`1.ResolveWithin(IContext parent) in c:\Projects\Ninject\ninject\src\Ninject\Planning\Targets\Target.cs:line 165
at Ninject.Activation.Providers.StandardProvider.GetValue(IContext context, ITarget target) in c:\Projects\Ninject\ninject\src\Ninject\Activation\Providers\StandardProvider.cs:line 114
at Ninject.Activation.Providers.StandardProvider.<>c__DisplayClass4.<Create>b__2(ITarget target) in c:\Projects\Ninject\ninject\src\Ninject\Activation\Providers\StandardProvider.cs:line 96
at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
at Ninject.Activation.Providers.StandardProvider.Create(IContext context) in c:\Projects\Ninject\ninject\src\Ninject\Activation\Providers\StandardProvider.cs:line 96
at Ninject.Activation.Context.Resolve() in c:\Projects\Ninject\ninject\src\Ninject\Activation\Context.cs:line 157
at Ninject.KernelBase.<>c__DisplayClass10.<Resolve>b__c(IBinding binding) in c:\Projects\Ninject\ninject\src\Ninject\KernelBase.cs:line 386
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
at Ninject.Web.Mvc.NinjectDependencyResolver.GetService(Type serviceType) in c:\Projects\Ninject\ninject.web.mvc\mvc3\src\Ninject.Web.Mvc\NinjectDependencyResolver.cs:line 56
at System.Web.Mvc.DefaultControllerFactory.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType)
--- End of inner exception stack trace ---
at System.Web.Mvc.DefaultControllerFactory.DefaultControllerActivator.Create(RequestContext requestContext, Type controllerType)
at System.Web.Mvc.DefaultControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType)
at System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName)
at System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory)
at System.Web.Mvc.MvcHandler.<>c__DisplayClass6.<BeginProcessRequest>b__2()
at System.Web.Mvc.SecurityUtil.<>c__DisplayClassb`1.<ProcessInApplicationTrust>b__a()
at System.Web.Mvc.SecurityUtil.<GetCallInAppTrustThunk>b__0(Action f)
at System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action)
at System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust[TResult](Func`1 func)
at System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state)
at System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContext httpContext, AsyncCallback callback, Object state)
at System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.BeginProcessRequest(HttpContext context, AsyncCallback cb, Object extraData)
at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
更新
以下是HomeController的代码：
public class HomeController : Controller
{
#region Declaration
public ICommonService _commonService { get; set; }
#endregion
#region Constructor
public HomeController()
{
}
public HomeController(ICommonService commonService)
{
this._commonService = commonService;
}
#endregion
public ActionResult Index()
{
return View();
}
CommonService和CommonRepository的构造函数：
public class CommonService : ICommonService
{
#region Declaration
private readonly ICommonRepository _repository;
#endregion
#region Constructor
public CommonService(ICommonRepository repository)
{
this._repository = repository;
}
#endregion
public class CommonRepository : ICommonRepository
{
#region Declaration
private DBContainer _context = new DBContainer();
#endregion
#region Constructor
public CommonRepository()
{
}
#endregion
我在这里缺少任何其他参考资料吗？
答案 0 :(得分：7)
这是Ninject中构造函数选择的工作原理：
在你的情况下，Ninject很可能不会选择无参数构造函数，因为它认为他知道如何解析ICommonService。如果您希望Ninject使用它或进一步调查ICommonService未解析的原因，请尝试使用[Inject]属性修饰无参数构造函数。
答案 1 :(得分：2)
如果您最近将MVC应用程序从.NET 4.0重新定位到4.5或其他方式，那么您会得到完全相同的症状。它通过引用目标的正确.NET版本DLL来修复。
如果您正在使用Ninject，Ninject.MVC3和Ninject.Web.Common，那么您将在那里找到所有.NET目标。
答案 2 :(得分：1)
引自https://github.com/ninject/ninject/wiki/Injection-Patterns：
主要DI模式是构造函数注入。当激活Ninject类型的实例时，将按顺序应用以下规则来选择要使用的类型构造函数之一： -
如果构造函数具有[Inject]属性，则使用它（但是如果将该属性应用于多个属性，Ninject将在检测时在运行时抛出NotSupportedException。）
如果没有构造函数具有[Inject]属性，Ninject将选择Ninject理解如何解析的参数最多的那个。
如果没有定义构造函数，Ninject将选择默认的无参数构造函数（假设有一个）。