[BUG] ValidationContext's Validations property is always empty about reactiveui.validation

[StanleyGoldman]

Can confirm workaround works: https://github.com/StanleyGoldman/UnderstandReactiveUIProblem/tree/validation-fix

GitHub

StanleyGoldman/UnderstandReactiveUIProblem

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[glennawatson]

Hi @Micha-kun are you able to provide a small repository with a sample of your problem?

[Micha-kun]

Hi @glennawatson I filled about the bug with new info. I'll try to make that repository later and share with you.

Thank you

[Micha-kun]

Here is the repository sample:

https://github.com/Micha-kun/ReactiveUI.Validation.BugTest

GitHub

Micha-kun/ReactiveUI.Validation.BugTest

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[Micha-kun]

I found that if I create the ValidationContext instance with RxApp.TaskpoolScheduler, it works as expected. By default it uses RxApp.MainThreadScheduler and, with this scheduler it doesn't refresh... Maybe in WinForms it requires to use TaskpoolScheduler as default?

[miqueljuan]

I found the same problem working in WPF, if i use the ValidationContext with RxApp.TaskpoolScheduler on my abstract class it works as expected, else throws ArgumentOutOfRangeException.

Without using an abstract class, with all the properties declared on the validated ViewModel it works with RxApp.MainThreadScheduler.

Special Characteristics:

• ReactiveUI.Validation version is 1.2.1
• Project target .NET Framework 4.7.2
• WPF project is a C# project.
• ViewModel project is a C# project.

[StanleyGoldman]

I recently hit this issue and I have a repro: https://github.com/StanleyGoldman/UnderstandReactiveUIProblem/tree/validation

GitHub

StanleyGoldman/UnderstandReactiveUIProblem

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[kagerouttepaso]

If you set the ViewModel after resolving the main thread queue, no exception will occur.

    internal class Program
    {
        [STAThread]
        public static void Main()
        {
            var app = new App();
            var vm = new MainWindowViewModel();
            var window = new MainWindowView();

            Service.DoEvennts();
            window.ViewModel = vm;

            app.Run(window);
        }
    }

    public static class Service
    {
        [SecurityCritical]
        [SecurityPermission(SecurityAction.Demand, Flags = SecurityPermissionFlag.UnmanagedCode)]
        public static void DoEvennts()
        {
            DispatcherFrame frame = new DispatcherFrame();
            Dispatcher.CurrentDispatcher.BeginInvoke(DispatcherPriority.Background,
                new DispatcherOperationCallback(ExitFrames), frame);
            Dispatcher.PushFrame(frame);
        }

        public static object ExitFrames(object f)
        {
            ((DispatcherFrame)f).Continue = false;
            return null;
        }
    }

[kagerouttepaso]

I want IObservableList to be published as a public property.For simple collection access, you can use IObservableList .Items.
The problem of scheduler is caused by using ReadOnlyObservableCollection .I think that scheduler-aware coding, including creation of ReadOnlyObservableCollection, should be done by library users.
Currently I use the following extension methods for binding to a View.

public static IObservable<IList<ValidationState>> ResolveValidationStatusChanges<TViewModel, TViewModelProperty>(
    this TViewModel vm,
    Expression<Func<TViewModel, TViewModelProperty>> viewModelProperty,
    bool exclusively = true)
       where TViewModel : ReactiveObject, IValidatableViewModel
{
    var field = typeof(ValidationContext).GetField("_validationSource", BindingFlags.InvokeMethod | BindingFlags.NonPublic | BindingFlags.Instance);
    var sourcelist = (SourceList<IValidationComponent>)field.GetValue(vm.ValidationContext);
    IObservableList<IValidationComponent> observableList = sourcelist.AsObservableList();

    return observableList
        .Connect()
        .ToCollection()
        .Select(c => Observable.CombineLatest(c
            .OfType<BasePropertyValidation<TViewModel, TViewModelProperty>>()
            .Where(x => x.ContainsProperty(viewModelProperty, exclusively))
            .Select(x => x.ValidationStatusChange)))
        .Switch();
}

ViewModel.ResolveValidationStatusChanges(x => x.IpAddress)
    .Select(x => string.Join(",", x.Where(b => !b.IsValid).SelectMany(b => b.Text)))
    .ObserveOn(RxApp.MainThreadScheduler)
    .BindTo(this, v => v._test.Text)
    .DisposeWith(d);

[worldbeater]

This should have been fixed in #82. With ReactiveUI.Validation from the main branch, the ArgumentOutOfRangeException is no longer thrown in BindValidation, and the ValidationContext is performing as expected, at least in my WPF playground 🎉 Feel free to reopen if you stumble upon this again.

[github-actions]

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