ResolutionFailedException與Unity

Question

我正在使用Patterns and Practices的Unity向我的對象中注入依賴關係，並且遇到了一個奇怪的問題（對我來說）。這裏是我的類定義：

public class ImageManager : IImageManager 
{ 
    IImageFileManager fileManager; 

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

    } 
} 

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

，這裏是註冊我的班

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

我原來在後面的代碼解決這個代碼（我知道，這違背了目的多多包涵。）的像這樣的XAML文件

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

它工作。但是我爲我的主視圖創建了一個視圖模型，並且當我將同一行復制到其中時，出現異常。這裏有兩個最內部異常：

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: 

我不知道是什麼問題，因爲的ImageManager顯然具有公共構造函數。我認爲這可能是由於一個無效的路徑，但如果我具體實例化對象，一切正常。

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

，如果我需要在新InjectionConstructor傳遞我也想知道（typeof運算（字符串））當我註冊IImageManager，但它似乎並沒有幫助，爲什麼現在會而不是之前需要呢？所以我很難過。這是我第一次使用依賴注入的嘗試，所以它可能是一些基本的東西。雖然我只是沒有看到什麼。

Answer 1

我在使用this article的例子作爲我的指導。要麼介紹中的示例過於先進，要麼出現錯誤信息。

經過諮詢其他來源（主要是PluarlSight）後，我想出了一個更簡單，更合乎邏輯的解決方案。

container.RegisterInstance<TimerViewModel>(new TimerViewModel()); 
container.RegisterType<IPieceImageManager, PieceImageManager>(); 
container.RegisterType<IImageFileManager, ImageFileManager> 
    (new InjectionConstructor("/images")); 
container.RegisterType<IImageManager, ImageManager>(); 

Answer 2

仔細查看錯誤消息。注意這個部分：

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

注意該類型名稱是IImageManager，不的ImageManager。沿線的某處你失去了你的類型映射。

您的註冊FileImageManager也有問題，因爲您沒有在註冊中指定文件夾參數，所以Unity不知道要傳遞哪個字符串。