mvvm-toolkit

Apply [ObservableProperty] to a private field inside a partial class inheriting from ObservableObject. The generator creates a public property with change notification, so a field named `name` becomes a `Name` property with optional OnNameChanged hooks.

Annotate an async Task method that accepts a CancellationToken with [RelayCommand(IncludeCancelCommand = true)]. The toolkit generates an IAsyncRelayCommand plus a paired cancel command whose CanExecute tracks the running state.

MVVMTK0008 means the containing class, or an enclosing type for nested classes, is not declared partial. The source generator emits a sibling partial declaration, so every level of the type hierarchy must include the partial keyword.

ObservableObject is the default base providing INotifyPropertyChanged and SetProperty. ObservableValidator adds INotifyDataErrorInfo for form validation, and ObservableRecipient adds IMessenger integration. C# single inheritance means you pick one and compose the others.

The command's CanExecute is not re-evaluated when the bound property changes. Add [NotifyCanExecuteChangedFor(nameof(SaveCommand))] to the observable field so the generator calls NotifyCanExecuteChanged automatically on every change.

Yes, the toolkit targets netstandard2.0, netstandard2.1, and net6.0+, so the same ViewModel patterns work across WPF, WinUI 3, MAUI, Uno Platform, and Avalonia. Only the XAML binding syntax and app bootstrap differ per framework.