ViewModels & Commands

In a Zafiro-based application, ViewModels should be functional, reactive, and resilient.

Reactive ViewModels

Use ReactiveObject as the base class. Properties should be defined using the [Reactive] attribute (from ReactiveUI.SourceGenerators) for brevity.

public partial class MyViewModel : ReactiveObject
{
    [Reactive] private string name;
    [Reactive] private bool isBusy;
}

Observation and Transformation

Use WhenAnyValue to react to property changes:

this.WhenAnyValue(x => x.Name)
    .Select(name => !string.IsNullOrEmpty(name))
    .ToPropertyEx(this, x => x.CanSubmit);

Enhanced Commands

Zafiro uses IEnhancedCommand, which extends ICommand and IReactiveCommand with additional metadata like Name and Text.

Creating a Command

Use ReactiveCommand.Create or ReactiveCommand.CreateFromTask and then Enhance() it.

public IEnhancedCommand Submit { get; }

public MyViewModel()
{
    Submit = ReactiveCommand.CreateFromTask(OnSubmit, canSubmit)
        .Enhance(text: "Submit Data", name: "SubmitCommand");
}

Error Handling

Use HandleErrorsWith to automatically channel command errors to the NotificationService.

Submit.HandleErrorsWith(uiServices.NotificationService, "Submission Failed")
    .DisposeWith(disposable);

Disposables

Always use a CompositeDisposable to manage subscriptions and command lifetimes.

public class MyViewModel : ReactiveObject, IDisposable
{
    private readonly CompositeDisposable disposables = new();

    public void Dispose() => disposables.Dispose();
}

Tip

Use .DisposeWith(disposables) on any observable subscription or command to ensure proper cleanup.

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