[Bug] RelayCommand does not update CanExecute status

[JavierMarcuzzi]

Description

I am performing it on Net Maui, Mac and iOS, they fail, on Android it usually works. On windows I did not test it.

I will copy the code so you can reproduce it.

I enter the first name, then the last name, but I add one letter less to the first name so that it does not meet the validation rule, then I add the correct, ie, one more letter to name, so the validation is correct, but the button no longer works. And if I use the version with CanShow, it does not update its status on the screen, it does not react to changes in the number of letters, but internally it is detected and writes the message according to the result. It is easier to reproduce it than to explain it. You can see that the button with the text try Save Valida Command does not work the second time, when everything is valid, if I close and open the program it works but only the first time.

Reproduction Sample file UI

public class MainPageCSharpMarkupValidationfluentDI : ContentPage
{
int count = 0;
readonly vmPersona _vm;

    public MainPageCSharpMarkupValidationfluentDI(vmPersona vm)
    {
        BindingContext = _vm = vm;

        var mi_scrollView = new ScrollView();
        var mi_verticalStacklayout = new VerticalStackLayout
        {
            Spacing = 25,
            Children =
            {
                new Label
                {
                    Text="Validacion C# Markpu DI!",
                }
                .Font(size: 32).CenterHorizontal(),

                 new Label().Bind(Label.TextProperty, nameof(vm.Mensaje)),
                 new Label().Bind(Label.TextProperty, (nameof(vm.CanShow)).ToString()),
                  new Button()
                             .Text("ver si esta forma anda")
                             .BindCommand(nameof(vm.ShowCommand))
                             .CenterHorizontal(),

                 new Entry()
                {
                    Keyboard = Keyboard.Chat,
                    BackgroundColor = Colors.AliceBlue,
                }.FontSize(15)
                .Placeholder("Enter name")
                .TextColor(Colors.Black)
                .Height(44)
                .Margin(5, 5)
                .Bind(Entry.TextProperty, nameof(vm.Nombre)),

                 new Label().Bind(Label.TextProperty, nameof(vm.Nombre)),

                 new HorizontalStackLayout
                 {
                     Children=
                     {
                        new VerticalStackLayout
                         {
                             Children=
                            {
                                new Label {Text="First Name"},
                                new Entry().FontSize(15)
                                .Placeholder("First Name")
                                .TextColor(Colors.Black)
                                .Height(44)
                                .Margin(5, 5)
                                .Width(300)
                                .Bind(Entry.TextProperty, nameof(vm.FirstName)),

                                new Label().Bind(Label.TextProperty, nameof(vm.FirstName)),

                            }
                         },
                        new VerticalStackLayout
                         {
                             Children=
                            {
                                new Label {Text="Last Name"},
                                new Entry()
                                .FontSize(15)
                                .Placeholder("last Name")
                                .TextColor(Colors.Black)
                                .Height(44)
                                .Margin(5, 5)
                                .Width(300)
                                .Bind(Entry.TextProperty, nameof(vm.LastName)),

                                new Label().Bind(Label.TextProperty, nameof(vm.LastName)),

                              
                            }
                         }

                     }
                 }.CenterHorizontal(),
                     new VerticalStackLayout
                         {
                             Children=
                            {
                             new Button()
                             .Text("try Save Valida Command")
                             .BindCommand(nameof(vm.SaveValidaCommand))
                             .CenterHorizontal()
                            }
                         },

                new Label().Bind(Label.TextProperty, nameof(vm.FullName)),
                 new Label().Bind(Label.TextProperty, nameof(vm.FullNameValida)),


                new Label{Text="Ver respuesta de Validación Fluent ....."}
                .Font(size: 24, bold:true).CenterHorizontal(),

                new Label{Text="ErrorMensajePasa", TextColor=Colors.BlueViolet},
                new Label().Bind(Label.TextProperty, nameof(vm.ErrorMensajePasa)),
                 new Label{Text="ErrorMensajeGeneral", TextColor=Colors.BlueViolet},
                new Label().Bind(Label.TextProperty, nameof(vm.ErrorMensajeGeneral)),
                 new Label{Text="FirtNameError", TextColor=Colors.BlueViolet},
                new Label().Bind(Label.TextProperty, nameof(vm.FirtNameError)),
                 new Label{Text="LastNameError", TextColor=Colors.BlueViolet},
                new Label().Bind(Label.TextProperty, nameof(vm.LastNameError)),


                new Label{Text="Fin respuesta Validación, inicio para ver si anda el mvvm ..."}
                .Font(size: 24, bold:true).CenterHorizontal(),

                new Button()
                .Text("Valida Excecute SingUpCommand")
                .Font(bold: true)
                .BindCommand(nameof(vm.ExecuteSignUpCommand))
                .CenterHorizontal(),

            }
        }.Paddings(30, 30, 30, 30);

        mi_scrollView.Content = mi_verticalStacklayout;
        Content = mi_scrollView;
    }

}

Reproduction Sample file FluentValidation

public class vPersona : AbstractValidator
{
public vPersona()
{
RuleFor(x => x.Name).NotNull().Length(5, 20).NotEqual("Javier");
RuleFor(x => x.Surname).NotNull().Length(4, 20);
}
}
public class mPersona
{
public string Name { get; set; }
public string Surname { get; set; }
}

Reproduction Sample file mvvm

public partial class vmPersona : ObservableObject
{
public mPersona PersonaObj { get; set; }
private readonly vPersona _validator;

    public vmPersona()
    {
        _validator = new vPersona();
    }

    [ObservableProperty]
   // [AlsoNotifyChangeFor(nameof(ExecuteSignUpCommand))]
    [NotifyCanExecuteChangedFor(nameof(ExecuteSignUpCommand))]
    //  [AlsoNotifyChangeFor(nameof(MensajeValidaNombre))]
    string nombre;


    [ObservableProperty]
    [NotifyPropertyChangedFor(nameof(FullName))]
    // [AlsoNotifyChangeFor(nameof(FullName))]
    //  [NotifyCanExecuteChangedFor(nameof(validaNuevoJavier))]
    [NotifyCanExecuteChangedFor(nameof(ShowCommand))]
    private string firstName = string.Empty;

    [ObservableProperty]
    [NotifyPropertyChangedFor(nameof(FullName))]
    //[AlsoNotifyChangeFor(nameof(FullName))]
    //      [NotifyPropertyChangedFor(nameof(validaNuevoJavier))]
    [NotifyCanExecuteChangedFor(nameof(ShowCommand))]
    private string lastName = string.Empty;

    public string FullName => $"{FirstName} {LastName}";

    [ObservableProperty]
    [NotifyPropertyChangedFor(nameof(FullNameValida))]
    //[AlsoNotifyChangeFor(nameof(FullNameValida))]
    [NotifyCanExecuteChangedFor(nameof(SaveValidaCommand))]
    //  [NotifyCanExecuteChangedFor(nameof(validaNuevoJavier))]
    private string firstNameValida = string.Empty;

    [ObservableProperty]
    [NotifyPropertyChangedFor(nameof(FullNameValida))]
   // [AlsoNotifyChangeFor(nameof(FullNameValida))]
    [NotifyCanExecuteChangedFor(nameof(SaveValidaCommand))]
    //      [NotifyPropertyChangedFor(nameof(validaNuevoJavier))]
    private string lastNameValida = string.Empty;

    public string FullNameValida => $"{FirstNameValida} {LastNameValida}";


    [RelayCommand(CanExecute = nameof(CanSaveExecute), IncludeCancelCommand = true)]
   // [ICommand(CanExecute = nameof(CanSaveExecute), IncludeCancelCommand = true)]
    private async Task SaveValidaAsync(CancellationToken cancelToken)
    {
        // Code to save the user details  ....  CanSaveExecute
        await Task.FromResult(0);
    }

    private bool CanSaveExecute()
  => !string.IsNullOrWhiteSpace(FirstName) && !string.IsNullOrWhiteSpace(LastName);

    [ObservableProperty]
    string errorMensajePasa = string.Empty;

    [ObservableProperty]
    string errorMensajeGeneral = string.Empty;


    [ObservableProperty]
    string firtNameError = string.Empty;

    [ObservableProperty]
    string lastNameError = string.Empty;

   
    // [ICommand]
    [RelayCommand]
    async Task ExecuteSignUpAsync()
    {
        await Shell.Current.DisplayAlert("Probar botón!",
               $"Parece que anda", "OK");

        PersonaObj = new mPersona
        {
            Name = FirstName,
            Surname = LastName
        };
        var validationResult = _validator.Validate(PersonaObj);
        if (validationResult.IsValid)
        {
            ErrorMensajePasa = "Validation Success..!!";
            ErrorMensajeGeneral = string.Empty;
        }
        else
        {
            ErrorMensajePasa = "Validation Failes..!!";

            ErrorMensajeGeneral = validationResult.ToString();

          //  var nError = validationResult.Errors.Where(e => e.PropertyName.Contains("Name"));
            var nError = validationResult.Errors.Where(e => e.PropertyName.Contains(nameof(PersonaObj.Name)));
            var sError = validationResult.Errors.Where(e => e.PropertyName.Contains("Surname"));

            foreach (var item in nError)
            {
                FirtNameError = item.ErrorMessage + Environment.NewLine;
            }

            foreach (var item in sError)
            {
                LastNameError = item.ErrorMessage + Environment.NewLine;
            }
        }
    }

    public bool CanShow { get => firstName.Length > 2 && lastName.Length > 2; }

    [ObservableProperty]
    string mensaje = string.Empty;

    //  [ICommand(CanExecute = nameof(CanShow))]
    [RelayCommand(CanExecute = nameof(CanShow))]
    private void Show()
    {
        //  MessageBox.Show(FullName);
        Mensaje = FullName;
    }

    partial void OnFirstNameChanged(string value)
    {
        if (CanShow)
        {
            //                MessageBox.Show($"Execute Custom code on {value}");
            Mensaje = $"Execute Custom code on {value}";
        }
    }

}

Steps to Reproduce

1. In field Name, write Javier, this is not valid name.
2. Click
3. In field Name, write JavierX, this is valid name.
4. Click don't work6.
   6 The first button, change status, but, status word don't change.

Reproduction imagery

[TheCodeTraveler]

Transferring this Issue to CommunityToolkit/dotnet

[Sergio0694]

That's... A lot of code 😅
@JavierMarcuzzi Can you share a minimal repro, possibly with no MAUI code involved?

[JavierMarcuzzi]

Dear Sergio Pedri Yes, I share the code on GitHub, but I don't know why, it doesn't allow me to upload it automatically, so I did it manually. Yes, in https://github.com/JavierMarcuzzi/netMauiMvvmProblem <https://github.com/JavierMarcuzzi/netMauiMvvmProblem> I did not copy the obj, bin, platform folder. I reverted the files to a previous version, anyway, it is commented, just remove the "//" and you can try it. The last thing, that is, the last option in shell, where it is pure c#, is not finished, it occurred to me to write without marking and return to the stable version, to test the problem. If you play a little with the validations, you will see that the button does not allow a second chance. But for this I think you should put everything in community.mvvm beta. For example: [ICommand] // [RelayCommand] async Task ExecuteSignUpAsync() { await valida(); } Translated with www.DeepL.com/Translator (free version)

…

El 15 jun. 2022, a las 12:55, Sergio Pedri ***@***.***> escribió: That's... A lot of code 😅 @JavierMarcuzzi <https://github.com/JavierMarcuzzi> Can you share a minimal repro, possibly with no MAUI code involved? — Reply to this email directly, view it on GitHub <#316 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACHUKHDWVD7ZREIJQVT4SPLVPH4HLANCNFSM5Y3WNZ5A>. You are receiving this because you were mentioned.

[Sergio0694]

Hey @JavierMarcuzzi, that is a full blown project, not a minimal repro. I don't even have the MAUI SDK installed 😅
Can you please share a minimal, self-contained repro, possibly with no MAUI references?

If you need a reference, this is an example of a good minimal repro that can help us investigate: #283.
Essentially, a small, self-contained snippet we can use to reproduce the issue.

Thank you! 🙂

[JavierMarcuzzi]

Dear Sergio Pedri I wouldn't know how to make a minimal example, the solution basically uses mvvm and markup, both from Community Toolkit. To put it somehow, if the validation is the first time, everything works correctly, but if the validation is incorrect because the word entered in the form does not meet the validation rules, when correcting the word entered the validation would be correct, but the button does not work, and as RelayCommand generates CanExecute, I suspect that the problem is generated by this way, but I do not know how to separate the problem of the form that asks me, at this moment I am writing a new form removing community markup and then I will remove community mvvm, this way I can isolate the part that gives problems. This is what I can do according to my knowledge, I am a veterinarian, not a software engineer, I use computer science for what today they would say data scientist. Thank you for your answer, not all important people answer the mails. Regards Javier Marcuzzi Translated with www.DeepL.com/Translator (free version)

…

El 16 jun. 2022, a las 08:38, Sergio Pedri ***@***.***> escribió: Hey @JavierMarcuzzi <https://github.com/JavierMarcuzzi>, that is a full blown project, not a minimal repro. I don't even have the MAUI SDK installed 😅 Can you please share a minimal, self-contained repro, possibly with no MAUI references? If you need a reference, this is an example of a good minimal repro that can help us investigate: #283 <#283>. Essentially, a small, self-contained snippet we can use to reproduce the issue. Thank you! 🙂 — Reply to this email directly, view it on GitHub <#316 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACHUKHBRM3IHGZ7VNSQBJWLVPMG3XANCNFSM5Y3WNZ5A>. You are receiving this because you were mentioned.

[Sergio0694]

To clarify why I'm asking for a minimal repro - the thing is that having to test a full project requires time, and often it's not even an actual problem with the MVVM Toolkit, but just either something caused by another framework (eg. MAUI, etc.), or just the user doing something wrong. Not having a minimal repro makes triaging issues particularly expensive for us, and our time is just limited (also because many of us juggle multiple projects at the same time). Let me know how that experiment goes 🙂

@brminnick since you're more familiar with MAUI, maybe you could help take a quick look?
I'm happy to help triage this once we have a more restricted repro I can use with just .NET stuff 👍

"Thank you for your answer, not all important people answer the mails."

I wouldn't say that, we're all just trying to help over here, no worries 😊

[wesleyscaldwell]

https://github.com/wesleyscaldwell/CommToolKitRelayCommandCanExecute

Trial & Step 1:

• If you click button 1 first you'll see button 2 is disabled but doesn't grey out.
  Trial & Step 2:
• Close App and start again : Click button 2 first - Button 2 is disabled and greyed out
  * Issue: the same binding event results in two different outputs

I have the issue in Maui - which was excluded per the above request.
BUT - i do seem to get different results in the maui app.
In maui, after clicking Button 1 >>> I am still able to click button two.

[Sergio0694]

@wesleyscaldwell Are you able to write a unit test for this? Like, a standalone method, with no UI framework dependencies, that just clearly expresses exactly what logic you expect and what assert is failing according to how you think this should work. That would help a lot 🙂

For reference, something exactly like this:

dotnet/tests/CommunityToolkit.Mvvm.UnitTests/Test_RelayCommand.cs

Lines 15 to 40 in 96517ea

	public void Test_RelayCommand_AlwaysEnabled()
	{
	int ticks = 0;
	RelayCommand? command = new(() => ticks++);
	Assert.IsTrue(command.CanExecute(null));
	Assert.IsTrue(command.CanExecute(new object()));
	(object?, EventArgs?) args = default;
	command.CanExecuteChanged += (s, e) => args = (s, e);
	command.NotifyCanExecuteChanged();
	Assert.AreSame(args.Item1, command);
	Assert.AreSame(args.Item2, EventArgs.Empty);
	command.Execute(null);
	Assert.AreEqual(ticks, 1);
	command.Execute(new object());
	Assert.AreEqual(ticks, 2);
	}