RzR.Validation.Attributes.Mvvm 3.0.0.6710

MVVM integration for RzR.Validation.Attributes. It gives you ValidatableObservableObject -an INotifyPropertyChanged + INotifyDataErrorInfo base class that validates your view-model properties with the core DataAnnotations attributes.

There's no WPF or UI-framework dependency (INotifyDataErrorInfo lives in System.ComponentModel), so the same base works with WPF, WinUI, .NET MAUI, and Avalonia.

Install

dotnet add package RzR.Validation.Attributes.Mvvm

It pulls in the core RzR.Validation.Attributes package. Targets netstandard2.0.

Define a view-model

Derive from ValidatableObservableObject, decorate the properties with the core attributes, and back each setter with SetProperty:

using RzR.Validation.Attributes.Attributes.Require;
using RzR.Validation.Attributes.Attributes.Identity;
using RzR.Validation.Attributes.Attributes.Greater;
using RzR.Validation.Attributes.Mvvm;

public class PersonViewModel : ValidatableObservableObject
{
    private string _name;
	
    [ValRequiredNotEmpty]
    public string Name
    {
        get => _name;
        set => SetProperty(ref _name, value);
    }

    private string _email;
	
    [ValEmail]
    public string Email
    {
        get => _email;
        set => SetProperty(ref _email, value);
    }

    private int _age;
	
    [ValGreaterThan(0)]
    public int Age
    {
        get => _age;
        set => SetProperty(ref _age, value);
    }
}

Setting a property runs the attributes on that property and raises both PropertyChanged and ErrorsChanged, so the UI updates as the user types.

Binding to errors (WPF)

<TextBox Text="{Binding Email,
                        UpdateSourceTrigger=PropertyChanged,
                        ValidatesOnNotifyDataErrors=True,
                        NotifyOnValidationError=True}" />

The messages come straight from the attributes and surface through INotifyDataErrorInfo, so WPF shows them with its default error template. WinUI, .NET MAUI, and Avalonia also consume INotifyDataErrorInfo: bind as you normally would and each renders the errors in its own way.

Reading errors in code

var vm = new PersonViewModel { Email = "not-an-email" };

bool hasErrors = vm.HasErrors; // true
var emailErrors = vm.GetErrors(nameof(vm.Email)); // messages for Email
vm.ErrorsChanged += (sender, e) => { /* e.PropertyName */ };

GetErrors(null) returns every current error across the object.

Validate before saving

SetProperty validates only the property being set. Before you commit, call ValidateAll() to run everything — including class-level and cross-property attributes like ValRequiredIf or ValAtLeastOneOf:

if (vm.ValidateAll())
{
    // no errors, safe to save
}

If you need to validate a value outside of a setter, ValidateProperty(value, propertyName) is public.

Notes

• The rules live on your view-model properties as the core Val* attributes; this base just triggers them.
• netstandard2.0, no WPF/UI dependency, usable from any INotifyDataErrorInfo host.