c# - ResolutionFailedException 与 Unity

Question

我正在使用 Patterns and Practices 的 Unity 将依赖项注入(inject)我的对象，并且遇到了一个奇怪的(无论如何对我来说)问题。这是我的类定义:

public class ImageManager : IImageManager 
{
    IImageFileManager fileManager;

    public ImageManager(IImageFileManager fileMgr)
    {
        this.fileManager = fileMgr;

    }
}

public class ImageFileManager : IImageFileManager
{
    public ImageFileManager(string folder)
    {
        FileFolder = folder;
    }
 }

这是注册我的类(class)的代码

container.RegisterInstance<MainWindowViewModel>(new MainWindowViewModel())
         .RegisterType<IPieceImageManager, PieceImageManager>(
              new InjectionConstructor(typeof(string)))
         .RegisterType<IImageFileManager, ImageFileManager>()
         .RegisterType<IImageManager, ImageManager>(
              new InjectionConstructor(typeof(IImageFileManager)));

我最初在像这样的 XAML 文件的后面的代码中解决了这个问题(我知道，它违背了目的。请耐心等待。)

IImageManager imageManager = MvvmViewModelLocator.Container.Resolve<IImageManager>(
    new ParameterOverride("folder", "/images"));

它奏效了。但是我为我的主视图创建了一个 View 模型，当我将同一行复制到其中时，出现异常。这是两个最内部的异常:

InnerException: Microsoft.Practices.Unity.ResolutionFailedException
  HResult=-2146233088
  Message=Resolution of the dependency failed, type = "SwapPuzzleApp.Model.IImageManager", name = "(none)".
Exception occurred while: while resolving.
Exception is: InvalidOperationException - The type IImageManager does not have an accessible constructor.

At the time of the exception, the container was:

Resolving SwapPuzzleApp.Model.IImageManager,(none)

        Source=Microsoft.Practices.Unity
        TypeRequested=IImageManager
        StackTrace:
             at Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, Object existing, String name, IEnumerable`1 resolverOverrides)
             at Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, String name, IEnumerable`1 resolverOverrides)
             at Microsoft.Practices.Unity.UnityContainer.Resolve(Type t, String name, ResolverOverride[] resolverOverrides)
             at Microsoft.Practices.Unity.UnityContainerExtensions.Resolve[T](IUnityContainer container, ResolverOverride[] overrides)
             at SwapPuzzleApp.ViewModel.MainWindowViewModel..ctor() in c:\Users\Carole\Documents\Visual Studio 2012\Projects\SwapPuzzle\SwapPuzzle\ViewModel\MainWindowViewModel.cs:line 17
             at SwapPuzzleApp.ViewModel.MvvmViewModelLocator..cctor() in c:\Users\Carole\Documents\Visual Studio 2012\Projects\SwapPuzzle\SwapPuzzle\ViewModel\MvvmViewModelLocator.cs:line 51
        InnerException: System.InvalidOperationException
             HResult=-2146233079
             Message=The type IImageManager does not have an accessible constructor.
             Source=Microsoft.Practices.Unity
             StackTrace:

             StackTrace:
                  at Microsoft.Practices.ObjectBuilder2.DynamicMethodConstructorStrategy.ThrowForNullExistingObject(IBuilderContext context)
                  at lambda_method(Closure , IBuilderContext )
                  at Microsoft.Practices.ObjectBuilder2.DynamicBuildPlanGenerationContext.<>c__DisplayClass1.<GetBuildMethod>b__0(IBuilderContext context)
                  at Microsoft.Practices.ObjectBuilder2.DynamicMethodBuildPlan.BuildUp(IBuilderContext context)
                  at Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp(IBuilderContext context)
                  at Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp(IBuilderContext context)
                  at Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, Object existing, String name, IEnumerable`1 resolverOverrides)
             InnerException: 

我不确定问题出在哪里，因为 ImageManager 显然有一个公共(public)构造函数。我认为这可能是由于路径无效，但如果我具体实例化该对象，一切正常。

// this line has no problems
IImageManager imageManager = new ImageManager(new ImageFileManager("/images"));  

我也想知道我注册IImageManager时是否需要传入new InjectionConstructor(typeof(string))，但它似乎没有帮助，为什么现在而不是以前需要它？所以我很难过。这是我第一次尝试使用依赖注入(inject)，所以它可能是一些基本的东西。不过，我只是没看到什么。

Answer 1

仔细查看错误消息。注意这部分:

 Message=The type IImageManager does not have an accessible constructor.

请注意类型名称是 IImageManager，不是 ImageManager。沿线的某个地方，您丢失了类型映射。

你的 FileImageManager 注册也有问题，因为你没有在注册中指定文件夹参数，所以 Unity 不知道要传递什么字符串。