How to solve the Simple Injector error "the instance is requested outside the context of an active (Async Scoped) scope" in WPF with MVVM?

Question

I have application written in WPF and MVVM and I've used Simple Injector as IoC Container. My main view model has constructor in that I inject bll class:

public MainWindowViewModel(IReviewBodyBLL reviewBodyBLL)
{
    this.reviewBodyBLL = reviewBodyBLL;

and this view model is setup in MainWindow:

public partial class MainWindow : Window
{
    public MainWindow(MainWindowViewModel viewModel)
    {
        InitializeComponent();

        base.DataContext = viewModel;

and all classes are registered:

container.Register<IFreewayReviewCreatorDbContext, FreewayReviewCreatorDbContext>(Lifestyle.Scoped);
container.Register<IUnitOfWorkFactory, UnitOfWorkFactory>(Lifestyle.Scoped);
container.Register<IUnitOfWork, UnitOfWork>(Lifestyle.Scoped);
container.Register<IReviewBodyBLL, ReviewBodyBLL>(Lifestyle.Transient);

// Register your windows and view models:
container.Register<MainWindow>();
container.Register<MainWindowViewModel>();

and I get error when I try to run application:

Exception thrown: 'SimpleInjector.ActivationException' in SimpleInjector.dll

The program '[28028] FreewayReviewCreator.exe' has exited with code 0 (0x0).

Application stop without any break.

When I remove from main view model constructor IReviewBodyBLL reviewBodyBLL application start correctly. How to inject bll to the constructor?

Please post the full exception details, i.e. exception type, exception message, and stack trace of the exception and *all* its inner exceptions. — Steven, Dec 09 '19 at 15:03
Where and how are you instantiating the `MainWindowViewModel`? — mm8, Dec 09 '19 at 15:24
MainWindowViewModel is instantiating in the constructor public MainWindow(MainWindowViewModel viewModel) — Robert, Dec 11 '19 at 08:11
@Steven: UnitOfWorkFactory is registered using the 'Async Scoped' lifestyle, but the instance is requested outside the context of an active (Async Scoped) scope. I have changed Scope to Transient for UnitOfWorkFactory because it isn't disposable and now it works, thanks — Robert, Dec 11 '19 at 09:37

score 0 · Accepted Answer · answered Dec 11 '19 at 10:53

For a WPF application, where you can have multiple windows open at the same time, where each window should run in its own scope, Simple Injector's ambient scoping model will not work, because it becomes unclear when to dispose a single scope, as there will typically always be a window open.

Instead, you can use Simple Injector's "flowing" scoping model, as described in this Q/A about Win Forms. This will work the same for WPF.

How to solve the Simple Injector error "the instance is requested outside the context of an active (Async Scoped) scope" in WPF with MVVM?

1 Answers1