IEntityChangeTracker的多个实例不能引用实体对象

Question

我开始在我的MVC5代码-第一应用程序中使用尼尼姆。这是我的NinjectWebCommon.cs：

private static IKernel CreateKernel()
    {
        var kernel = new StandardKernel();
        try
        {
            kernel.Bind<Func<IKernel>>().ToMethod(ctx => () => new Bootstrapper().Kernel);
            kernel.Bind<IHttpModule>().To<HttpApplicationInitializationHttpModule>();

            kernel.Bind<CMSContext>()
                .ToSelf()
                //.InSingletonScope();
                .InRequestScope();

            kernel.Bind<IExecutiveRepository>()
                .To<ExecutiveRepository>();

            kernel.Bind<IExecutiveSectionRepository>()
                .To<ExecutiveSectionRepository>();

            kernel.Bind<IExecutiveSectionMappingRepository>()
                .To<ExecutiveSectionMappingRepository>();

            kernel.Bind<IUserRepository>()
                .To<UserRepository>();

            kernel.Bind<IContentRepository>()
                .To<ContentRepository>();

            RegisterServices(kernel);
            return kernel;
        }
        catch
        {
            kernel.Dispose();
            throw;
        }
    }

我尝试了.InSingletonScope()和.InRequestScope()，但是仍然得到了‘实体对象不能被多个IEntityChangeTracker实例引用’错误。这是我的界面：

    public interface IExecutiveRepository : IDisposable
{
    IEnumerable<Executive> GetExecutives();
    Executive GetExecutiveById(int executiveId);
    void InsertExecutive(Executive executive);
    void UpdateExecutive(Executive executive);
    void DeleteExecutive(int executiveId);
    void Save();
}

这是我的混凝土：

 public class ExecutiveRepository : IExecutiveRepository, IDisposable
{
    private CMSContext context;

    public ExecutiveRepository(CMSContext context)
    {
        this.context = context;
    }

    public IEnumerable<Executive> GetExecutives()
    {
        return context.Executives.ToList();
    }

    public Executive GetExecutiveById(int id)
    {
        return context.Executives.Find(id);
    }

    public void InsertExecutive(Executive executive)
    {
        context.Executives.Add(executive);
    }

    public void DeleteExecutive(int executiveId)
    {
        Executive executive = context.Executives.Find(executiveId);
        context.Executives.Remove(executive);
    }

    public void UpdateExecutive(Executive executive)
    {
        context.Entry(executive).State = EntityState.Modified;
    }

    public void Save()
    {
        context.SaveChanges();
    }

    private bool disposed = false;

    protected virtual void Dispose(bool disposing)
    {
        if (!this.disposed)
        {
            if (disposing)
            {
                context.Dispose();
            }
        }
        this.disposed = true;
    }

    public void Dispose()
    {
        Dispose(true);
        GC.SuppressFinalize(this);
    }
}

这里是控制器(最相关的部分)：

 public class ExecutiveController : Controller
{
    private IExecutiveRepository executiveRepository;
    private IUserRepository userRepository;
    private IExecutiveSectionRepository executiveSectionRepository;
    private IExecutiveSectionMappingRepository executiveSectionMappingRepository;
    private IContentRepository contentRepository;
    private Ninject.IKernel _kernel = new StandardKernel();

    //[Inject]
    public ExecutiveController()
    {
        executiveRepository = _kernel.Get<ExecutiveRepository>();
        userRepository = _kernel.Get<UserRepository>();
        executiveSectionRepository = _kernel.Get<ExecutiveSectionRepository>();
        executiveSectionMappingRepository = _kernel.Get<ExecutiveSectionMappingRepository>();
        contentRepository = _kernel.Get<ContentRepository>();
    }
 ...

不知道我做错了什么，但在增加一个新的‘执行’it炸弹.我确实理解它试图使用不同的上下文，这就是问题所在，但我只是不知道如何修复它。显然，NinjectWebCommon.cs类中的一行：

 kernel.Bind<CMSContext>()
                .ToSelf()
                //.InSingletonScope();
                .InRequestScope();

应该是解决办法，但不是.有什么想法/建议吗？

Answer 1

如果您还没有使用NUGET Ninject.Web.Mvc，那么您应该使用它。这将配置您的应用程序，使其可以使用Ninject，而不是绑定。从我在CreateKernel()方法中可以看到的情况来看，您似乎已经相当熟悉绑定方面的内容了。

一旦您的绑定到位，您就不应该在控制器中创建内核，这是因为Ninject.Web.Mvc库将Ninject配置为在幕后为您创建控制器。因此，添加到它们中的任何依赖项都应该自动解决。

因此，可以使用构造函数注入来解决依赖关系：

public class ExecutiveController : Controller
{
    private IExecutiveRepository ExecutiveRepository;
    private IUserRepository UserRepository;
    private IExecutiveSectionRepository ExecutiveSectionRepository;
    private IExecutiveSectionMappingRepository ExecutiveSectionMappingRepository;
    private IContentRepository ContentRepository;

    public ExecutiveController(
         IExecutiveRepository executiveRepository,
         IUserRepository userRepository,
         IExecutiveSectionRepository executiveSectionRepository,
         IExecutiveSectionMappingRepository executiveSectionMappingRepository,
         IContentRepository contentRepository)
    {

         // Set the field values
         this.ExecutiveRepository = executiveRepository,
         this.UserRepository = userRepository,
         this.ExecutiveSectionRepository = executiveSectionRepository,
         this.ExecutiveSectionMappingRepository = executiveSectionMappingRepository,
         this.ContentRepository = contentRepository;
    }

    public ActionResult Index(int id)
    {
        // Use one of your dependencies...
        var executive = this.executiveRepository.GetExecutiveById(id);
    }
}

或者可以使用具有相同效果的[Inject]属性：

public class ExecutiveController : Controller
{
    [Inject]
    public IExecutiveRepository executiveRepository { get; set; }

    [Inject]
    public IUserRepository userRepository { get; set; }

    [Inject]
    public IExecutiveSectionRepository executiveSectionRepository { get; set; }

    [Inject]
    public IExecutiveSectionMappingRepository executiveSectionMappingRepository { get; set; }

    [Inject]
    public IContentRepository contentRepository { get; set; }

    public ExecutiveController()
    {

    }

    public ActionResult Index(int id)
    {
        // Use one of your dependencies...
        var executive = this.executiveRepository.GetExecutiveById(id);
    }
}

Answer 2

您正在为每个控制器创建一个内核。

InRequestScope只确保每个内核每个请求有一个实例。

因此，您需要调整内核的设置，以便每个web应用程序只有一个内核。请参见：

• Ninject.Web.Mvc
• 教程
• YouTube

Answer 3

这可能回答不了问题。但我倾向于使用EF为您提供的IDbContextFactory，并这样做：

public interface IDefaultContextFactory : IDbContextFactory<CMSContext> {}

public class DefaultContextFactory : IDefaultContextFactory 
{
    private readonly Lazy<CMSContext> lazyContext = new Lazy<CMSContext>(() => new CMSContext());

    public CMSContext Create() 
    {
        return lazyContext.Value;
    }
}

然后绑定它，当您需要上下文时，您可以这样做：

public class ExecutiveRepository : IExecutiveRepository, IDisposable
{
    private readonly CMSContext context;

    public ExecutiveRepository(IDefaultContextFactory contextFactory)
    {
        this.context = contextFactory.Create();
    }
}

我相信@BatteryBackupUnit是正确的，我也会考虑在上下文中使用上面的模式。