Resolution failed with error no public constructor is available for type

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:

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

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

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:

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:UsersCaroleDocumentsVisual Studio 2012ProjectsSwapPuzzleSwapPuzzleViewModelMainWindowViewModel.cs:line 17
             at SwapPuzzleApp.ViewModel.MvvmViewModelLocator..cctor() in c:UsersCaroleDocumentsVisual Studio 2012ProjectsSwapPuzzleSwapPuzzleViewModelMvvmViewModelLocator.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.

// 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.

Unity Container ResolutionFailedException when the mapping is correct in the config file

I was using a ServiceLocator which i was DIing with Unity

This all worked fine, but I wanted lazy instantiation of the repositories as they have quite sparse use.

So my ServiceLocator now looks like

I’m now getting a really unhelpful ResolutionFailedException error

Resolution of the dependency failed, type = «DomainModel.DataServices.Interface.IUserStore», name = «». Exception message is: The current build operation (build key Build Key[DomainModel.DataServices.Interface.IUserStore, null]) failed: The current type, DomainModel.DataServices.Interface.IUserStore, is an interface and cannot be constructed. Are you missing a type mapping? (Strategy type BuildPlanStrategy, index 3)

Telling me my interface type cannot be instantiated because it is an interface is pretty pointless. I know it’s an interface, that’s why the container is supposed to be resolving it for me!

Anyway, the point to note here is that I know the type mapping in the config is fine, as when I was injecting the type interface directly instead of trying to lazy load, it resolved it with no problems.

What am I missing that means something somewhere has to change in order to lazy load this way?

Update: I am guessing what’s happening here, is that when I DI the container into the ServiceLocator, the «main» container is instantiating a new container each time which is then not configured properly. I think maybe I need some way to specify that I was to pass this in as the container, rather than resolve it with a new instantiation.

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Resolution failed with error: No public constructor is available

I am using WCF web services and it was using OLD unity 2.0. So i updated Unity and other reference with latest version 5.0. I am getting exception:

Really i tried many things but not success. please any expert have a look.

1 Answer 1

I came across the same error upgrading from Unity version 3.5 to 5.11. In my case, during resolution the exception was the same ResolutionFailedException with message «No public constructor is available for IMyInterface» and having the same inner exception InvalidRegistrationException .

Well, the error messages and types of exceptions were misleading in my case; there was no registration problem nor did I ask for a public constructor for the interface. It seems that there has been a breaking change in the Resolve method overload which takes an instance name. Null names are no longer equivalent to empty string names. Replace your empty string name to null or use the other overload which doesn’t specify an instance name:

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Unity ResolutionFailedException for System.Web.Mvc Types

My WebApp is a combination of WebForms pages and MVC 4 pages.

Using Unity, I am getting the following exception.

Exception Type:

Message:

with an Inner Exception of:

Message:

Stack Trace:

I consistently get the same resolution exception for the following types:

In Application_Start, I am setting up the IoC with:

. where GetContainer returns all the registered types and UnityDependencyResolver is-a IDependencyResolver

Any ideas what is causing the issue?

1 Answer 1

I am not sure how the container instance returned by UnityConfigurator.GetContainer() behaves exactly, but I assume it tries to resolve by itself alone the ModelMetadataProvider when needed. This ModelMetadataProvider has some dependencies that your container does not know that only the initial MVC resolver can resolve. By ‘initial MVC resolver’ I mean the result of DependencyResolver.Current before you call DependencyResolver.SetResolver(. ) . So, you need to implement a proxy over your own container and use as fallback the initial MVC resolver.

A quick example of how the proxy’s implementation should look like:

And then, in Application_Start() you overwrite the MVC resolver with a instance of this proxy, like this:

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Unity’s ResolutionFailedException

I have an old Asp.Net web application using Unity for dependency injection. Today I updated the Unity using NuGet to the latest version. On trying to run the application, I am getting an exception:

Unity.Exceptions.ResolutionFailedException: ‘Resolution of the dependency failed, type = ‘SOME.Services.ISomeService’, name = ‘(none)’. Exception occurred while: while resolving. Exception is: InvalidOperationException — The property converter on type DAL.Repositories.SomeRepository is not settable.

The exception happened on line

I am very new to Unity. Could you please help?

1 Answer 1

The newer versions of Unity have breaking changes.
You may want to stick with the older versions of the DLL until you refactor the changes.

v4.0.1 Version 4.x is dead. Loss of original signing certificate made it impossible to release anything compatible with v4.0.1 release. To give original developers a credit only about 60 issues were found during two years in production. To move on and enable further development version v5 has been created.

v5.x Version 5.x is created as replacement for v4.0.1. Assemblies and namespaces are renamed and refactored but otherwise it is compatible with the original. v5.0.0 release fixes most of the issues found in v4.0.1 and implements several optimizations but the accent was on compatibility and if optimization would break API it was omitted. Once stabilized, this version will enter LTS status and will be patched and fixed for the next few years. There will be no significant development in this line.

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Unity + C# — «Resolution of the dependency failed»

My application have a 10 WCFService ( WCFService Application on platform .NET Framework 3.5) with same software and hardware but only 1 takes this exception:

When user is logged in invoke this method:

with GetRegisteredService() implementation with ClientIdentifier = 0 for first execution

with IOC code implementation and Initilization:

i have this exception on execution method «Resolve»:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. —> Microsoft.Practices.Unity.ResolutionFailedException: Resolution of the dependency failed, type = «ApCon.IService», name = «Anagxxx». Exception message is: The current build operation (build key Build Key[ApCon.StandardService, Anaxxxx]) failed: The current build operation (build key Build Key[ApCon.StandardService, Anaxxxx]) failed:Index was outside the bounds of the array. (Strategy type DynamicMethodConstructorStrategy, index 0) (Strategy type BuildPlanStrategy, index 3) —> Microsoft.Practices.ObjectBuilder2.BuildFailedException: The current build operation (build key Build Key[ApCon.StandardService, Anagrafe]) failed: The current build operation (build key Build Key[ApCon.StandardService, Anagrafe]) failed: Index was outside the bounds of the array. (Strategy type DynamicMethodConstructorStrategy, index 0) (Strategy type BuildPlanStrategy, index 3) —> Microsoft.Practices.ObjectBuilder2.BuildFailedException: The current build operation (build key Build Key[ApCon.StandardService, Anagxxx]) failed: Index was outside the bounds of the array. (Strategy type DynamicMethodConstructorStrategy, index 0) —> System.IndexOutOfRangeException: Index was outside the bounds of the array. at System.Collections.Generic.List1.Add(T item) at Microsoft.Practices.ObjectBuilder2.DependencyResolverTrackerPolicy.AddResolverKey(Object key) at Microsoft.Practices.ObjectBuilder2.ConstructorSelectorPolicyBase`1.CreateSelectedConstructor(IBuilderContext context, ConstructorInfo ctor) at Microsoft.Practices.ObjectBuilder2.ConstructorSelectorPolicyBase1.SelectConstructor(IBuilderContext context) at Microsoft.Practices.ObjectBuilder2.DynamicMethodConstructorStrategy.PreBuildUp(IBuilderContext context) at Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp(IBuilderContext context) — End of inner exception stack trace — at

Could it be the lock instruction? It seems that types weren’t registered and isInitialized becomed true

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I’m devolping a WPF application, using Prism 7.2. I have a module, which implements the IModule interface, where I register the views and viewmodels in the RegisterTypes method, e.g.:

containerRegistry.Register<IPanelOptimizationViewModel, PanelOptimizationViewModel>();

The problem arises when I try to resolve the implementation:

var vm = containerProvider.Resolve<IPanelOptimizationViewModel>();

whereupon I get the following Unity.ResolutionFailedException:
‘Resolution failed with error: No public constructor is available for type
XXX.Infrastructure.Interfaces.IView.’

The PanelOptimizationViewModel class derives from a base class:

public class PanelOptimizationViewModel : ViewModelBase, IPanelOptimizationViewModel
{
     public PanelOptimizationViewModel(IPanelOptimizationView view, IPanelOptimizationInputViewModel inpVM) : base(view)
}

and the ViewModelBase looks like this:

 public class ViewModelBase : BindableBase, IViewModel
 {
     public IView View { get; set; }

     public ViewModelBase(IView view)
     {
         View = view;
         View.ViewModel = this;
     }
 }

The interfaces IView and IViewModel are defined in a common Infrastructure project. They are not registered anywhere in the container, but if I remove the IPanelOptimizationInputViewModel parameter, no runtime exception is thrown — leading me to think that I don’t need to do this, either.

As far as I have been able to understand, the Unity.Container will use the «most parameterized» constructor (see Unity not using the default constructor of the class), but I cannot provide a parameter in the Register method to specify this, as one apparently could before (pre Prism 7’s container abstraction), with the RegisterType method.

How to solve this? Is there an overload of the Prism.Ioc.IContainerRegistry.Register method that allows me to set up the registration for constructor injection?

Should I work directly with the Unity container?

Basically, I am trying to inject a child view’s viewmodel into the constructor of my «main» viewmodel, but this does not go well as long as the wrong constructor is called on the base class, with the wrong set of parameters… (if that is what is happening).

Needless to say, all child views and viewmodels have been registered in the RegisterTypes method in the module.

Any help on this would be greatly appreciated