Data trigger does not trigger on data change.

[cris-m]

I was working on a way to validate data in dotnet maui viewmodel and xaml. But I am facing an issue, the data trigger does not trigger when an Entry has validation.
Here is the code.

// validation rule interface
public interface IValidationRule<T>
  {
      string ValidationMessage { get; set; }
      bool Check(T value);
  }

// validation object class
public class ValidatableObject<T> : INotifyDataErrorInfo
{
  private readonly List<IValidationRule<T>> _validations;
  private readonly ObservableCollection<string> _errors;
  private T _value;
  public List<IValidationRule<T>> Validations => _validations;
  public T Value
  {
      get => _value;
      set
      {
          _value = value;
          RaisePropertyChanged(nameof(Value));
          Validate();
      }
  }
  public ObservableCollection<string> Errors => _errors;
  public bool HasErrors => Errors.Any();

  public ValidatableObject(params IValidationRule<T>[] validation)
  {
      _errors = new ObservableCollection<string>();
      _validations = validation.ToList();
  }

  public event EventHandler<DataErrorsChangedEventArgs> ErrorsChanged;
  public event PropertyChangedEventHandler PropertyChanged;

public IEnumerable GetErrors(string propertyName)
{
if (string.IsNullOrEmpty(propertyName))
{
  return Errors;
}
return null;
}

  public bool Validate()
  {
      Errors.Clear();

      IEnumerable<string> errors = _validations.Where(v => !v.Check(Value))
          .Select(v => v.ValidationMessage);

      foreach (string error in errors)
      {
          Errors.Add(error);
      }
      RaiseErrorsChanged(nameof(Value));
      return Errors.Any();
  }
  private void RaiseErrorsChanged(string propertyName)
  {
      ErrorsChanged?.Invoke(this, new DataErrorsChangedEventArgs(propertyName));
  }
}

// view model
public partial class LoginViewModel: BaseViewModel
{
    [ObservableProperty]
    ValidatableObject<string> email;

    [ObservableProperty]
    ValidatableObject<string> password;

    public LoginViewModel()
    {

        Email = new ValidatableObject<string>(
            new RequiredValidationRule { ValidationMessage = "Email is required" },
            new EmailValidationRule { ValidationMessage = "Invalid email address" });

        Password = new ValidatableObject<string>(
            new RequiredValidationRule { ValidationMessage = "Password is required" });
    }

    [RelayCommand]
    void Login()
    {
        if (Email.Validate() && Password.Validate())
        {

        }
    }
}

<!-- view -->
 <VerticalStackLayout>

        <Entry Text="{Binding Email.Value, Mode=TwoWay}" 
           Placeholder="Email" 
           Keyboard="Email">
            <Entry.Triggers>
                <DataTrigger TargetType="Entry" 
                         Binding="{Binding Email.HasErrors, Mode=TwoWay}" 
                         Value="False">
                    <Setter Property="BackgroundColor" 
                        Value="Default"/>
                </DataTrigger>
                <DataTrigger TargetType="Entry" 
                         Binding="{Binding Email.HasErrors, Mode=TwoWay}" 
                         Value="True">
                    <Setter Property="BackgroundColor" 
                        Value="Red"/>
                    <Setter Property="TextColor" 
                        Value="Pink"/>
                </DataTrigger>
            </Entry.Triggers>
        </Entry>

        <Label Text="{Binding Email.Errors, Converter={StaticResource FirstValidationErrorConverter}}" 
           TextColor="Red" 
           IsVisible="{Binding Email.HasErrors}"/>


        <Entry Text="{Binding Password.Value}"
               Placeholder="Password"
               IsPassword="True">
            <Entry.Triggers>
                <DataTrigger TargetType="Entry" 
                         Binding="{Binding Password.HasErrors,  Mode=TwoWay}" 
                         Value="False">
                    <Setter Property="BackgroundColor" 
                        Value="Default"/>
                </DataTrigger>
                <DataTrigger TargetType="Entry" 
                         Binding="{Binding Password.HasErrors, Mode=TwoWay}" 
                         Value="True">
                    <Setter Property="BackgroundColor" 
                        Value="Red"/>
                    <Setter Property="TextColor" 
                        Value="Pink"/>
                </DataTrigger>
            </Entry.Triggers>
        </Entry>
        <Label Text="{Binding Password.Errors, Converter={StaticResource FirstValidationErrorConverter}}" 
           TextColor="Red" 
           IsVisible="{Binding Password.HasErrors}"/>

        <Button Text="Login"
                TextColor="White"
                BackgroundColor="Blue"
                Command="{Binding LoginCommand}"/>

    </VerticalStackLayout>

Event if the HasErrors is True theDataTrigger does not react. Any help?

[no149]

I am facing a similar issue.
<Style TargetType="Grid"> <Style.Triggers> <DataTrigger TargetType="CollectionView" Binding="{Binding IsBookSelected}" Value="True"> <Setter Property="BackgroundColor" Value="aqua"/> </DataTrigger> <DataTrigger TargetType="CollectionView" Binding="{Binding IsBookSelected}" Value="False"> <Setter Property="BackgroundColor" Value="Red"/> </DataTrigger> </Style.Triggers> </Style>

The IsBookSelected binding only works for the initial value, in this case it's false. The "true" trigger does not react after updating the observable property to true.

Is this a bug?