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 一起使用。我已经修改了我所有的控制器和业务 classes 以通过它们的构造函数接收它们的依赖项作为接口。

boostrapper class 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 NuGet 包首次安装它们时的状态相比没有任何变化。

当我启动 MVC 应用程序时，遇到以下错误消息：

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 class 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 Whosebug 上错误消息的问题。（到目前为止，None 的提议解决方案已经解决了这个问题，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

我找到了适合我的特定场景的解决方案，这有点令人惊讶。

我不得不推出自己的 DependencyResolver class 并使用它来代替 Unity 提供的 MVC 解析器。我写的解析器如下：

using System;
using System.Collections.Generic;
using System.Web.Mvc;

using Microsoft.Practices.Unity;

/// <summary>
/// Resolves dependencies against the current DI container.
/// </summary>
public class UnityDependencyResolver : IDependencyResolver
{
    /// <summary>
    /// The container
    /// </summary>
    private readonly IUnityContainer container;

    /// <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;
    }

    /// <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, if it can be resolved; otherwise, <c>null</c>.</returns>
    public object GetService(Type serviceType)
    {
        return this.container.IsRegistered(serviceType) 
            ? this.container.Resolve(serviceType) 
            : 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 this.container.ResolveAll(serviceType);
    }
}

最重要的部分是 GetService 的实现：它必须 return null 如果它不能解析类型，否则，MVC肚皮向上并抛出消息异常，"XXX is an interface, and can't be constructed. Are you missing a binding?"

这当然改变了 Bootstrapper.cs 中这行代码的行为：

DependencyResolver.SetResolver(
    new UnityDependencyResolver(UnityContainer));

它使用本地实现而不是默认的 Unity 实现。

奇怪的是，我从中提取的示例应用程序在我的机器上本地运行，而且它没有使用自定义解析器。没有这个 class 也能正常工作。我不知道为什么会这样，这很麻烦（我更喜欢确定性的问题答案），但此时我很高兴我可以重新开始工作。

Answer 2

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

中的代码

似乎在启动时有轻微的性能优势，但主要是您不会引发 10 个异常。

/// <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 
    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 接口之一，则可以使用

将其从排除列表中删除

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

Unity 4(IOC) + MVC 5 在启动期间无法解析类型

Unity 4(IOC) + MVC 5 unable to resolve types during startup

c#

asp.net-mvc

unity-container