C# Unity 的 ResolutionFailedException
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ResolutionFailedException with Unity
提问by VanillaBean
I'm using Patterns and Practices' Unity to inject dependencies into my objects and have hit a weird (to me, anyway) issue. Here's my class definitions:
我正在使用 Patterns and Practices 的 Unity 将依赖项注入到我的对象中，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;
}
}
And here's the code to register my classes
这是注册我的课程的代码
container.RegisterInstance<MainWindowViewModel>(new MainWindowViewModel())
.RegisterType<IPieceImageManager, PieceImageManager>(
new InjectionConstructor(typeof(string)))
.RegisterType<IImageFileManager, ImageFileManager>()
.RegisterType<IImageManager, ImageManager>(
new InjectionConstructor(typeof(IImageFileManager)));
I originally resolved this in the code behind (I know, it defeats the purpose. Bear with me.) of the XAML file like this
我最初在这样的 XAML 文件背后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"));
And it worked. But I created a view model for my main view and when I copied the same line into it, I get an exception. Here are the two most inner exceptions:
它奏效了。但是我为我的主视图创建了一个视图模型，当我将同一行复制到其中时，出现异常。以下是两个最内在的例外：
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:
I'm not sure what the problem is, as ImageManager clearly has a public constructor. I thought it might be due to an invalid path, but if I concretely instantiate the object, everything works.
我不确定问题是什么，因为 ImageManager 显然有一个公共构造函数。我认为这可能是由于路径无效，但是如果我具体实例化对象，则一切正常。
// this line has no problems
IImageManager imageManager = new ImageManager(new ImageFileManager("/images"));
I also wondered if I needed to pass in new InjectionConstructor(typeof(string)) when I register IImageManager, but it doesn't seem to help and why would it be needed now and not before? So I'm stumped. This is my first attempt at using Dependency Injection, so it's probably something basic. I'm just not seeing what, though.
我还想知道在注册 IImageManager 时是否需要传入 new InjectionConstructor(typeof(string))，但它似乎没有帮助，为什么现在而不是之前需要它？所以我很难过。这是我第一次尝试使用依赖注入，所以它可能是一些基本的东西。不过，我只是没有看到什么。
采纳答案by VanillaBean
I was using the examples in this articleas my guide. Either the examples in there are way too advanced for an introduction, or there's misinformation in that topic.
我使用本文中的示例作为指导。要么是那里的例子太先进而无法介绍，要么是该主题中存在错误信息。
After consulting other sources (mainly PluarlSight), I came up with a much simpler and more logical solution.
在咨询了其他来源（主要是 PluarlSight）之后，我想出了一个更简单、更合乎逻辑的解决方案。
container.RegisterInstance<TimerViewModel>(new TimerViewModel());
container.RegisterType<IPieceImageManager, PieceImageManager>();
container.RegisterType<IImageFileManager, ImageFileManager>
(new InjectionConstructor("/images"));
container.RegisterType<IImageManager, ImageManager>();
回答by Chris Tavares
Look very closely at the error message. Notice this part:
仔细查看错误消息。注意这部分：
Message=The type IImageManager does not have an accessible constructor.
Notice the type name is IImageManager, notImageManager. Somewhere along the line you lost your type mapping.
请注意，类型名称是 IImageManager，而不是ImageManager。在此过程中，您丢失了类型映射。
Your registration of FileImageManager has a problem as well, since you don't specify the folder parameter in the registration, so Unity has no idea what string to pass.
你的FileImageManager的注册也有问题，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。
