Forms

FormViewModel lives in Core and does not reference WinUI 3. WinUIFormViewModel adds INotifyDataErrorInfo. Field(name, value) creates a FormField<T>. Bind(field, propertyName, notifyCanExecute) wires the public property and CanExecute. When IDialogs is registered, leaving a dirty form confirms “Discard changes?”. Tests set DirtyNavigation = DirtyNavigationMode.SilentBlock. SubmitAsync(work) calls MarkClean() on success.

public sealed class ProductEditViewModel : WinUIFormViewModel
{
    private readonly FormField<string> _name;

    public ProductEditViewModel()
    {
        _name = Field("Name", "");
        Bind(_name, nameof(Name), () => SaveCommand.NotifyCanExecuteChanged());
    }

    public string Name
    {
        get => _name.Value ?? "";
        set => _name.Value = value;
    }

    private Task<Outcome> SaveAsync(CancellationToken ct) =>
        SubmitAsync(token => _catalog.SaveAsync(Name, token), cancellationToken: ct);
}