问为什么我的无参数ctor用Unity触发？
EN

Stack Overflow用户

提问于 2018-02-01 14:34:04

回答 1查看 59关注 0票数 0

我有一个名为TopMenuViewModel的ViewModel。它有两个构造器:一个没有参数，一个有应该从Unity推送的参数。

当我想使用视图模型时，注入不起作用，默认的无参数ctor被调用(不是注入的)，所以我不能使用依赖项。为什么和如何？:-)

下面是ViewModel：

public class TopMenuViewModel
{
    public int unreadMessagesCount { get; set; }
    public PersonnelAMEntity personnel { get; set; }
    IList<DocumentTypeEntity> quickDocumentTypes { get; set; }

    private readonly IPersonnelAMBusiness _IPersonnelAMBusinessRepo;
    private readonly IDocumentBusiness _IDocumentBusinessRepo;
    private readonly IMessageBusiness _IMessageBusinessRepo;

    [InjectionConstructor]
    public TopMenuViewModel(IPersonnelAMBusiness personnelRepo, IDocumentBusiness documentRepo, IMessageBusiness messageRepo)
    {
        _IPersonnelAMBusinessRepo = personnelRepo;
        _IDocumentBusinessRepo = documentRepo;
        _IMessageBusinessRepo = messageRepo;
    }

    public TopMenuViewModel() {}


    internal void SetMenuFor(int matricule)
    {
        // Get personnel
        this.personnel = _IPersonnelAMBusinessRepo.GetAll(matricule);

        // Get message number
        unreadMessagesCount = _IMessageBusinessRepo.GetUnreadReceivedMessages(this.personnel).Value.Count;

        // Get QuickDocumentTypes
        quickDocumentTypes = _IDocumentBusinessRepo.GetAllQuickDocumentTypes(SessionManager.visibilityUnit).Value;
    }
}

下面是它的名字：

public ActionResult TopMenu()
{
    TopMenuViewModel model = new TopMenuViewModel();
    model.SetMenuFor(SessionManager.matricule);
    return PartialView("~/Views/Shared/_TopMenu.cshtml", model);
}

当我调用SetMenuFor时，我在_IPersonnelAMBusinessRepo上得到了一个'System.NullReferenceException‘。

下面是UnityConfig (它是由编译器读取的，因为我可以在它上面设置断点(多亏了UnityMvcActivator才能触发)：

public static void RegisterTypes(IUnityContainer container)
{

    container.RegisterType<DbContext, ApplicationDbContext>(new HierarchicalLifetimeManager());
    container.RegisterType<UserManager<ApplicationUser>>(new HierarchicalLifetimeManager());
    container.RegisterType<IUserStore<ApplicationUser>, UserStore<ApplicationUser>>(new HierarchicalLifetimeManager());
    //container.RegisterType<AccountController>(new InjectionConstructor());
    container.RegisterType<AccountController>(new InjectionConstructor(typeof(IPersonnelAMBusiness)));

    // Business Layer DI
    container.RegisterType<IAMLogBusiness, AMLogBusiness>();    // No dependencies
    container.RegisterType<IAuditBusiness, AuditBusiness>();    // No dependencies
    container.RegisterType<ICockpitStatBusiness, CockpitStatsBusiness>();    // No dependencies
    container.RegisterType<IDistributionListBusiness, DistributionListBusiness>();  // No dependencies
    container.RegisterType<IEmailBusiness, EmailBusiness>();    // No dependencies
    container.RegisterType<INatureBusiness, NatureBusiness>();  // No dependencies
    container.RegisterType<IProfessionBusiness, ProfessionBusiness>();  // No dependencies
    container.RegisterType<IReportingBusiness, ReportingBusiness>();    // No dependencies
    container.RegisterType<IRequeteBusiness, RequeteBusiness>();    // No dependencies
    container.RegisterType<ISocieteBusiness, SocieteBusiness>();    // No dependencies
    container.RegisterType<ITopicBusiness, TopicBusiness>();    // No dependencies
    container.RegisterType<IUserBusiness, UserBusiness>();  // No dependencies
    container.RegisterType<IUnitBusiness, UnitBusiness>();    // No dependencies
    container.RegisterType<IDocumentBusiness, DocumentBusiness>();  // No dependencies
    container.RegisterType<IInstallationBusiness, InstallationBusiness>();  // Unit(V) dependencies
    container.RegisterType<IAnomalyBusiness, AnomalyBusiness>();    // Audit(V), Installation(V) dependencies UNIT
    container.RegisterType<IPersonnelAMBusiness, PersonnelAMBusiness>();    // Anomaly(V), profession(V), user(V), audit(V), Unit(V) dependencies
    container.RegisterType<IMessageBusiness, MessageBusiness>();    // Personnel(V), Document(V) Unity(V) dependencies

    // Set resolver
    DependencyResolver.SetResolver(new UnityDependencyResolver(container));

}

dependency-injection

asp.net-mvc

人脸识别特惠活动

精准实时的人脸检测、分析、识别等服务，在线、离线满足多样需求，可应用于智慧零售、智慧社区、在线娱乐等多种应用场景

回答 1

Stack Overflow用户

发布于 2018-02-03 08:34:28

当您在控制器操作中使用以下代码时：

TopMenuViewModel model = new TopMenuViewModel();

实际上，您并不是通过Unity Container创建ViewModel实例。您可以使用C# new运算符调用无参数构造函数来创建它。

要通过Unity创建ViewModel实例，请执行以下操作：

1.将ViewModel的实例注入您的控制器构造函数：

private readonly TopMenuViewModel _viewModel;

public YourController(TopMenuViewModel viewModel)
{
    if (viewModel == null)
    {
        throw new ArgumentNullException(nameof(viewModel));
    }

    _viewModel = viewModel;
}

请注意，控制器中不应该有其他构造函数。

2.删除TopMenu()操作中创建的TopMenuViewModel实例，使用保存在_viewModel字段中的注入实例：

public ActionResult TopMenu()
{
    _viewModel.SetMenuFor(SessionManager.matricule);
    return PartialView("~/Views/Shared/_TopMenu.cshtml", _viewModel);
}