尝试将MEF与MVC控制器一起使用时，CompositionContractMismatchException

我正在开发一个更大的C＃MVC 4项目，该项目分为几个程序集（Core，Domain，Backend MVC，Frontend MVC等） . 我使用MEF提供的插件架构来加载和解决大多数依赖项 . 现在我也想用它来加载MVC控制器 . 在几十个样本中发现了典型的场景 .

但我一直得到这个YSOD：

例外情况说：

[CompositionContractMismatchException: Cannot cast the underlying exported value of type "XY.HomeController (ContractName="XY.HomeController")" to type "XY.HomeController".]
System.ComponentModel.Composition.ExportServices.CastExportedValue(ICompositionElement element, Object exportedValue) +505573
System.ComponentModel.Composition.<>c__DisplayClass10`2.<CreateSemiStronglyTypedLazy>b__c() +62
System.Lazy`1.CreateValue() +14439352
System.Lazy`1.LazyInitValue() +91
  XY.DependencyManagement.SomeCustomControllerFactory.GetControllerInstance(RequestContext requestContext, Type controllerType) in (Path)\Core\DependencyManagement\SomeCustomControllerFactory.cs:32
System.Web.Mvc.DefaultControllerFactory.CreateController(RequestContext requestContext, String controllerName) +89
System.Web.Mvc.MvcHandler.ProcessRequestInit(HttpContextBase httpContext, IController& controller, IControllerFactory& factory) +305
System.Web.Mvc.MvcHandler.BeginProcessRequest(HttpContextBase httpContext, AsyncCallback callback, Object state) +87
System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +12550291
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +288

自定义ControllerFactory：

public class SomeCustomControllerFactory : DefaultControllerFactory {

    private readonly CompositionContainer _compositionContainer;

    public SomeCustomControllerFactory (CompositionContainer compositionContainer) {
        _compositionContainer = compositionContainer;
    }

    protected override IController GetControllerInstance(RequestContext requestContext, Type controllerType) {
        var export = _compositionContainer.GetExports(controllerType, null, null).SingleOrDefault();

        IController result;

        if (export != null) {
            result = export.Value as IController;
        } else {
            result = base.GetControllerInstance(requestContext, controllerType);
            _compositionContainer.ComposeParts(result);
        }

        return result;
    }

 protected override Type GetControllerType(RequestContext requestContext, string controllerName) {

        Type controllerType = base.GetControllerType(requestContext, controllerName);

 // used to find objects in the container which assemblies are in a sub directory and not discovered by MVC
 // TODO: only create parts that are used
        if (controllerType == null && this._compositionContainer != null &&
            this._compositionContainer != null) {

            var controllerTypes =
                this._compositionContainer.GetExports<Controller, IDictionary<string, object>>()
                    .Where(
                        e =>
                        e.Value.GetType().Name.ToLowerInvariant() ==
                        controllerName.ToLowerInvariant() + ControllerNameByConvention)
                    .Select(e => e.Value.GetType()).ToList();

            switch (controllerTypes.Count) {
                case 0:
                    controllerType = null;
                    break;
                case 1:
                    controllerType = controllerTypes.First();
                    break;
                case 2:
                    throw CreateAmbiguousControllerException(requestContext.RouteData.Route, controllerName,
                                                             controllerTypes);
            }
        }

        return controllerType;
    }

和CustomDependencyResolver：

public class CustomDependencyResolver : IDependencyResolver {

    private readonly CompositionContainer _container;
    public CustomDependencyResolver(CompositionContainer container) {
        _container = container;
 }
    public IDependencyScope BeginScope() {
        return (IDependencyScope)this;
    }

    public object GetService(Type serviceType) {
        var export = _container.GetExports(serviceType, null, null).SingleOrDefault();

        return null != export ? export.Value : null;
    }

    public IEnumerable<object> GetServices(Type serviceType) {
        var exports = _container.GetExports(serviceType, null, null);
        var createdObjects = new List<object>();

        if (exports.Any()) {
            foreach (var export in exports) {
                createdObjects.Add(export.Value);
            }
        }

        return createdObjects;
    }

一切都以这种方式配置DependencyResolver.SetResolver（new CustomDependencyResolver（container））; ControllerBuilder.Current.SetControllerFactory（new SomeCustomControllerFactory（container））;

附注：使用MEF2 RegistrationBuilder和带有三个AssemblyCatalog和一个DirectoryCatalog的AggregateCatalog .

如果我从主项目解决方案中提取它并创建一个新的mvc 4互联网项目解决方案并将其集成在那里，那么整个过程非常有效 . （使用一个程序集测试它，使用第二个简单的核心库 . ）

我已经打开了CompositionOptions.DisableSilentRejection . 并发现此资源调试MEF相关错误https://blogs.msdn.com/b/dsplaisted/archive/2010/07/13/how-to-debug-and-diagnose-mef-failures.aspx?Redirected=true我删除了HomeController中的所有内容（空构造函数，没有导入等） . MEF容器装有合适的出口 . 一切都很好 .

经过一整天的调试和研究，我学到了很多关于MEF的知识，但仍然遇到了同样的问题 . 希望有人能在这里给我一个暗示想要的错误 . 将所有内容移动到新的MVC项目会非常非常耗时:-(

谢谢！