WPF-UserControl with the .NET library FluentValidation

Question

I use WPF with MVVM and for validation the .NET library FluentValidation (https://github.com/FluentValidation). With a TextBox and a simple validation

RuleFor(x => x.Name).NotEmpty().WithMessage("No empty name.");

It works. If the text box is empty then the frame and the field turn red. The validation does not work with a UserControl that also only has a TextBox for testing. Frame and field do not turn red. I get not a message.

I can't find anything in the documentation about validation with a UserControl. Does anyone have experience with this and can give me a tip?

Answer 1

In WPF is important to use AdornerDecorator in xaml. Did you use it?

<AdornerDecorator>
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>

        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="Auto" />
            <ColumnDefinition />
            <ColumnDefinition Width="Auto" />
        </Grid.ColumnDefinitions>

        <TextBlock Grid.Row="0" Grid.Column="0" Margin="3" Text="Name: " />
        <TextBox Grid.Row="0" Grid.Column="1"
                 Text="{Binding Name, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
        <TextBlock Grid.Row="0" Grid.Column="2" Margin="3" MaxWidth="150" TextWrapping="Wrap"
                   Text="Name not empty, not equal 'foo' and max length is 16" />


        <TextBlock Grid.Row="1" Grid.Column="0" Margin="3" Text="Surname: " />
        <TextBox Grid.Row="1" Grid.Column="1"
                 Text="{Binding Surname, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
        <TextBlock Grid.Row="1" Grid.Column="2" Margin="3" MaxWidth="150" TextWrapping="Wrap"
                   Text="Surname should be equal 'foo'" />


        <TextBlock Grid.Row="2" Grid.Column="0" Margin="3" Text="Phone number: " />
        <TextBox Grid.Row="2" Grid.Column="1"
                 Text="{Binding PhoneNumber, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
        <TextBlock Grid.Row="2" Grid.Column="2" Margin="3" MaxWidth="150" TextWrapping="Wrap"
                   Text="Phone number required and allow from 9 to 12 digits" />
    </Grid>
</AdornerDecorator>

Also you can use library https://github.com/Karnah/ReactiveValidation which has fluent-interface and build-in MVVM support. Sample:

public class CarViewModel : ValidatableObject
{
    public CarViewModel()
    {
        Validator = GetValidator();
    }

    private IObjectValidator GetValidator()
    {
        var builder = new ValidationBuilder<CarViewModel>();

        builder.RuleFor(vm => vm.Make).NotEmpty();
        builder.RuleFor(vm => vm.Model).NotEmpty().WithMessage("Please specify a car model");
        builder.RuleFor(vm => vm.Mileage).GreaterThan(0).When(model => model.HasMileage);
        builder.RuleFor(vm => vm.Vin).Must(BeAValidVin).WithMessage("Please specify a valid VIN");
        builder.RuleFor(vm => vm.Description).Length(10, 100);

        return builder.Build(this);
    }

    private bool BeAValidVin(string vin)
    {
        // Custom vin validating logic goes here.
    }

    // Properties with realization INotifyPropertyChanged goes here.
}

Here quick start for WPF applications: https://github.com/Karnah/ReactiveValidation/wiki/WPF.-Quick-start