c# - Unity 4(IOC) + MVC 5 在启动期间无法解析类型

Question

我将 Unity 4(通过 NuGet)与 ASP.NET MVC 5 结合使用。我修改了所有 Controller 和业务类，以通过它们的构造函数接收它们的依赖项作为接口(interface)。

boostrapper 类包含以下代码:

public class Bootstrapper
{
    public static IUnityContainer UnityContainer { get; set; }

    public static void Initialize()
    {
        InitializeUnity();
        RegisterTypes();
    }

    private static void InitializeUnity()
    {
        UnityContainer = UnityConfig.GetConfiguredContainer();
        DependencyResolver.SetResolver(new UnityDependencyResolver(UnityContainer));
    }

    private static void RegisterTypes()
    {
        new Core.Bootstrapper().RegisterTypes(UnityContainer);
    }
}

Core.Bootstrapper().RegisterTypes的内容如下:

public IUnityContainer RegisterTypes(IUnityContainer container)
{
    // Register repositories
    container.RegisterType<IRepository, Repository>()
             .RegisterType<IBdeRepository, BdeRepository>()
             .RegisterType<IDocumentRepository, DocumentRepository>()
             .RegisterType<IHampRepository, HampRepository>()
             .RegisterType<IReportsRepository, ReportsRepository>()
             .RegisterType<ITransactionRepository, TransactionRepository>();

    // Register commands
    container.RegisterType<IBaseCommand, BaseCommand>()
             .RegisterType<IDailyLetterInfoUpdate, DailyLetterInfoUpdate>()
             .RegisterType<IDailyReconciliation, DailyReconciliation>()
             .RegisterType<InsertNewRows, InsertNewRows>()
             .RegisterType<IOrderDailyLM023, OrderDailyLM023>()
             .RegisterType<IOrderMonthlyLM012, OrderMonthlyLM012>()
             .RegisterType<IOrderMonthlyLM014, OrderMonthlyLM014>()
             .RegisterType<IPerformMonthlyRecastStatusUpdate, PerformMonthlyRecastStatusUpdate>()
             .RegisterType<IUpdateReissuedRecasts, UpdateReissuedRecasts>();

    // Register utility types
    container.RegisterType<ICsvExporter, CsvExporter>()
             .RegisterType<ILogger, Logger>();

    return container;
}

最后，UnityConfig.cs 和 UnityMvcActivator.cs 与它们首次由 NuGet 包安装时的状态相比保持不变。

当我启动我的 MVC 应用程序时，我遇到了以下错误消息:

Resolution of the dependency failed, type = "System.Web.Mvc.ITempDataProviderFactory", name = "(none)".

Exception occurred while: while resolving.

Exception is: InvalidOperationException - The current type, System.Web.Mvc.ITempDataProviderFactory, is an interface and cannot be constructed. Are you missing a type mapping?

它提到的类似乎是 MVC 本身内部的东西，这让我相信我在配置 Unity 时错过了一些东西，或者我在这样做时搞砸了一些东西。然而，对于我的生活，我无法弄清楚它是什么，尽管我已经咨询了几乎所有我能找到的关于 StackOverflow 上错误消息的问题。 (到目前为止，所提出的解决方案都没有解决问题，但很可能我遗漏了一些东西。)

谁能看到我忽略的东西？我做错了什么？

更新:

这里抛出异常:

public static void RegisterRoutes(RouteCollection routes)
{
    routes.IgnoreRoute("{resource}.axd/{*pathInfo}");

    routes.MapMvcAttributeRoutes(); // Exception thrown on this line.
}

Answer 1

这里有一个略有不同的实现，其中对 MVC 部分进行了特定排除，改编自 UnityDependencyResolver.cs 处的代码。

似乎在启动时有轻微的性能优势，但主要是您不会引发 10 次异常。

/// <summary>
/// Resolves dependencies against the current DI container.
/// </summary>
public class UnityDependencyResolver : IDependencyResolver
{
    private readonly IUnityContainer container;
    // NB Not likely to be be big but will be frequent so use HashSet as O(1) lookup cost - see https://stackoverflow.com/questions/18651940/performance-benchmarking-of-contains-exists-and-any
    private readonly HashSet<Type> excludedTypes;

    /// <summary>
    /// Initializes a new instance of the <see cref="UnityDependencyResolver"/> class.
    /// </summary>
    /// <param name="container">The container.</param>
    public UnityDependencyResolver(IUnityContainer container)
    {
        this.container = container;
        excludedTypes = new HashSet<Type>();

        StandardExclusions();
    }

    /// <summary>
    /// Resolves an instance of the default requested type from the container.
    /// </summary>
    /// <param name="serviceType">The <see cref="Type"/> of the object to get from the container.</param>
    /// <returns>The requested object.</returns>
    public object GetService(Type serviceType)
    {
        if (typeof(IController).IsAssignableFrom(serviceType))
        {
            return container.Resolve(serviceType);
        }

        try
        {
            return excludedTypes.Contains(serviceType) ? null : container.Resolve(serviceType);
        }
        catch (ResolutionFailedException)
        {
            return null;
        }
    }

    /// <summary>
    /// Resolves multiply registered services.
    /// </summary>
    /// <param name="serviceType">The type of the requested services.</param>
    /// <returns>The requested services.</returns>
    public IEnumerable<object> GetServices(Type serviceType)
    {
        return container.ResolveAll(serviceType);
    }

    public void Exclude<T>()
    {
        Exclude(typeof(T));
    }

    public void Exclude(Type type)
    {
        excludedTypes.Add(type);
    }

    public void Include<T>()
    {
        Include(typeof(T));
    }

    public void Include(Type type)
    {
        excludedTypes.Remove(type);
    }

    private void StandardExclusions()
    {
        Exclude<System.Web.Mvc.IControllerFactory>();
        Exclude<System.Web.Mvc.IControllerActivator>();
        Exclude<System.Web.Mvc.ITempDataProviderFactory>();
        Exclude<System.Web.Mvc.ITempDataProvider>();
        Exclude<System.Web.Mvc.Async.IAsyncActionInvokerFactory>();
        Exclude<System.Web.Mvc.IActionInvokerFactory>();
        Exclude<System.Web.Mvc.Async.IAsyncActionInvoker>();
        Exclude<System.Web.Mvc.IActionInvoker>();
        Exclude<System.Web.Mvc.IViewPageActivator>();
        Exclude<System.Web.Mvc.ModelMetadataProvider>();
    }
}

如果您确实覆盖了标准 MVC 接口(interface)之一，那么您可以使用以下命令将其从排除列表中删除

var resolver = new UnityDependencyResolver(container);
resolver.Include<System.Web.Mvc.IActionInvoker>();