Autofac: Missing Method Involving MvvmLight RelayCommand

I have a generic collection class based on the MvvM Light library which I've registered with Autofac:

public class DialogCollection<TViewModel> : ObservableCollection<TViewModel>, IDialogCollection<TViewModel> 
{
    private readonly IUIManager _uiManager;

    public DialogCollection( IUIManager uiManager )
    {
        _uiManager = uiManager ?? throw new NullReferenceException( nameof(uiManager) );

        ViewModelSelectedCommand = new RelayCommand<TViewModel>( DetailItemSelectedHandler );
        AddNewViewModelCommand = new RelayCommand( AddNewItemHandler );
    }

    public RelayCommand<TViewModel> ViewModelSelectedCommand { get; }
    public RelayCommand AddNewViewModelCommand { get; }
}

Autofac registration:

builder.RegisterGeneric( typeof(DialogCollection<>) )
    .As( typeof(IDialogCollection<>) );

IUIManager, the only argument to the DialogCollection constructor, is also registered with Autofac, and is properly instantiated when the program runs.

The specific instance of IDialogCollection is generated from a lambda method created by Autofac, which is passed in thru the constructor of a class which holds an instance of the collection I want to create:

public class CommunitiesModel
{
    private readonly Func<IDialogCollection<CommunityModel>> _colBuilder;
    private readonly Func<CommunityModel> _communityBuilder;

    private DialogCollection<CommunityModel> _communities;

    public CommunitiesModel( 
        Func<IDialogCollection<CommunityModel>> colBuilder,
        Func<CommunityModel> commmunityBuilder
        )
    {
        _colBuilder = colBuilder ?? throw new NullReferenceException(nameof(colBuilder));
        _communityBuilder= commmunityBuilder?? throw new NullReferenceException(nameof(commmunityBuilder));
    }

    // I'm not showing how Load() gets called, but it does :)
    public override void Load()
    {
        // this next line creates an instance of DialogCollection
        // it's also where the Autofac Missing Method exception gets thrown
        Communities = (DialogCollection<CommunityModel>) _colBuilder();
    }
}

Both colBuilder and communityBuilder are properly instantiated when passed into the CommunitiesModel constructor, which I presume means Autofac was able to use the registration information to create methods that create instances of those classes.

I don't understand why there's a missing method exception when _colBuilder() is executed, since the code compiles fine (meaning the RelayCommand ctor is known and available).

If I comment out the two RelayCommand creation lines (i.e., "new RelayCommand...") in the definition of DialogCollection<>, the exception is not thrown.

Which means the Autofac creator method is gacking on not finding something inside a constructor which has already been called with the appropriate constructur arguments.

Here is the exception that gets thrown:

Autofac.Core.DependencyResolutionException HResult=0x80131500
Message=An error occurred during the activation of a particular registration. See the inner exception for details. Registration: Activator = DialogCollection1 (ReflectionActivator), Services =[WpfFramework.IDialogCollection1[[Olbert.CommunityScanner.Manager.ViewModel.CommunityModel, CommunityScannerManager, Version=0.0.0.1, Culture=neutral, PublicKeyToken=null]]], Lifetime = Autofac.Core.Lifetime.CurrentScopeLifetime, Sharing = None, Ownership = OwnedByLifetimeScope Source=Autofac StackTrace: at Autofac.Core.Resolving.InstanceLookup.Activate(IEnumerable1 parameters) at Autofac.Core.Resolving.InstanceLookup.Execute()
at Autofac.Core.Resolving.ResolveOperation.GetOrCreateInstance(ISharingLifetimeScope currentOperationScope, IComponentRegistration registration, IEnumerable1 parameters) at Autofac.Core.Resolving.ResolveOperation.Execute(IComponentRegistration registration, IEnumerable1 parameters) at Autofac.Core.Lifetime.LifetimeScope.ResolveComponent(IComponentRegistration registration, IEnumerable1 parameters) at Olbert.CommunityScanner.Manager.ViewModel.CommunitiesModel.Load() in C:\Programming\CommunityScanner\CommunityScannerManager\ViewModel\CommunitiesModel.cs:line 58 at Olbert.CommunityScanner.Manager.ViewModel.AppStateModel.set_ActivePageInfo(PageInfo value) in C:\Programming\CommunityScanner\CommunityScannerManager\ViewModel\AppWide\AppStateModel.cs:line 117 at Olbert.CommunityScanner.Manager.App.OnStartup(StartupEventArgs e) in C:\Programming\CommunityScanner\CommunityScannerManager\App.xaml.cs:line 44 at System.Windows.Application.<.ctor>b__1_0(Object unused) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.DispatcherOperation.InvokeImpl() at System.Windows.Threading.DispatcherOperation.InvokeInSecurityContext(Object state) at MS.Internal.CulturePreservingExecutionContext.CallbackWrapper(Object obj) at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) in f:\dd\ndp\clr\src\BCL\system\threading\executioncontext.cs:line 954
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) in f:\dd\ndp\clr\src\BCL\system\threading\executioncontext.cs:line 901
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) in f:\dd\ndp\clr\src\BCL\system\threading\executioncontext.cs:line 890
at MS.Internal.CulturePreservingExecutionContext.Run(CulturePreservingExecutionContext executionContext, ContextCallback callback, Object state) at System.Windows.Threading.DispatcherOperation.Invoke() at System.Windows.Threading.Dispatcher.ProcessQueue() at System.Windows.Threading.Dispatcher.WndProcHook(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled) at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o) at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs) at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler) at System.Windows.Threading.Dispatcher.LegacyInvokeImpl(DispatcherPriority priority, TimeSpan timeout, Delegate method, Object args, Int32 numArgs) at MS.Win32.HwndSubclass.SubclassWndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam) at MS.Win32.UnsafeNativeMethods.DispatchMessage(MSG& msg) at System.Windows.Threading.Dispatcher.PushFrameImpl(DispatcherFrame frame) at System.Windows.Threading.Dispatcher.PushFrame(DispatcherFrame frame)
at System.Windows.Application.RunDispatcher(Object ignore) at System.Windows.Application.RunInternal(Window window) at System.Windows.Application.Run(Window window) at System.Windows.Application.Run() at Olbert.CommunityScanner.Manager.App.Main()

Inner Exception 1: DependencyResolutionException: An exception was thrown while invoking the constructor 'Void .ctor(WpfFramework.IUIManager)' on type 'DialogCollection`1'.

Inner Exception 2: MissingMethodException: Method not found: 'Void GalaSoft.MvvmLight.Command.RelayCommand1..ctor(System.Action1)'.

I can provide more details if needed; what I've shown here is abstracted from a larger code base, but hopefully shows the relevant details.

I would recommend looking at RelayCommand1 - it appears IUIManager or DialogCollection<T> needs that constructor and it's not there. Work bottom up on this. The Autofac part is red herring. Meat of the issue is the inner exception at the bottom.