ObservableValidator with subclasses

[himadrinath]

i have main view model also two classes in this viewmodel

always false if i send FullName blank

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using System.ComponentModel.DataAnnotations;

public partial class TestViewModel : ObservableValidator
    {
        public TestViewModel() {
            user= new User();
            address= new Address();

        }
        User? user;

        public User User
        {
            get { return user; }
            set => SetProperty(ref user, value, true);
        }

        Address? address;

        public Address Address
        {
            get { return address; }
            set => SetProperty(ref address, value, true);
        }

        [RelayCommand]
        void Submit()
        {
            ValidateAllProperties();
            if (HasErrors)
           //always false
        }

    }

    public partial class User : ObservableValidator
    {
        string? fullName;

        [Required(ErrorMessage = "FullName Required!", AllowEmptyStrings = false)]
        [MinLength(2)]
        [MaxLength(60)]
        public string? FullName
        {
            get { return fullName; }
            set => SetProperty(ref fullName, value, true);
        }
    }

    public partial class Address : ObservableValidator
    {
        string? location;

        [Required(ErrorMessage = "Location Required!", AllowEmptyStrings = false)]
        [MinLength(2)]
        [MaxLength(100)]
        public string? Location
        {
            get { return location; }
            set => SetProperty(ref location, value, true);
        }
    }

[Sergio0694]

You're trying to validate TestViewModel, but this type has no validatable properties. Validation doesn't automatically handle nested properties, you'll have to either call the validation on both nested properties manually and forward the errors, or write some custom attribute that will implement the validation for a nested viewmodel. The fact you're currently not seeing errors is expected 🙂

[himadrinath]

@Sergio0694 thanks

[nivle]

@Sergio0694 Is it possible to add a new function, that actually validates all properties including the nested properties?

[CodingOctocat]

@Sergio0694 How to implement it? I tried to write a ForwardErrorsAttribute:

public class ForwardErrorsAttribute : ValidationAttribute
{
    public override bool IsValid(object? value)
    {
        return !((INotifyDataErrorInfo)value).HasErrors;
    }
}

But the code will not be executed.

---

Update Edit:

I found a solution:

[ForwardErrors]
public SubclassProperty SubclassProperty
{
    get => _subclassProperty;
    set
    {
        if (EqualityComparer<SubclassProperty>.Default.Equals(_subclassProperty, value))
        {
            return;
        }

        OnPropertyChanging();

        // Unregister oldValue events。
        _subclassProperty.PropertyChanging -= SubclassPropertyChanging;
        _subclassProperty.PropertyChanged -= SubclassPropertyChanged;
        _subclassProperty.ErrorsChanged -= SubclassProperty_ErrorsChanged;

        // Ensure newValue register events。
        value.ErrorsChanged -= SubclassProperty_ErrorsChanged;
        value.ErrorsChanged += SubclassProperty_ErrorsChanged;
        value.PropertyChanging -= SubclassPropertyChanging;
        value.PropertyChanging += SubclassPropertyChanging;
        value.PropertyChanged -= SubclassPropertyChanged;
        value.PropertyChanged += SubclassPropertyChanged;

        _subclassProperty= value;

        OnPropertyChanged();
    }
}

private void SubclassProperty_ErrorsChanged(object? sender, DataErrorsChangedEventArgs e)
{
    ValidateProperty(SubclassProperty, nameof(SubclassProperty));
}