[Signal("customSignal", NetVariantType.String)] // You can define signals that Qml can listen to.
public class QmlType
{
    /// <summary>
    /// Properties are exposed to Qml.
    /// </summary>
    [NotifySignal("stringPropertyChanged")] // For Qml binding/MVVM.
    public string StringProperty { get; set; }

    /// <summary>
    /// Methods can return .NET types.
    /// The returned type can be invoked from Qml (properties/methods/events/etc).
    /// </summary>
    /// <returns></returns>
    public QmlType CreateNetObject()
    {
        return new QmlType();
    }

    /// <summary>
    /// Qml can pass .NET types to .NET methods.
    /// </summary>
    /// <param name="parameter"></param>
    public void TestMethod(QmlType parameter)
    {
    }

    /// <summary>
    /// Qml can also pass Qml/C++ objects that can be invoked from .NET
    /// </summary>
    /// <param name="qObject"></param>
    public void TestMethodWithQObject(dynamic qObject)
    {
        string result = qObject.PropertyDefinedInCpp;
        qObject.MethodDefinedInCpp(result);
    }
    
    /// <summary>
    /// Async methods can be invoked with continuations happening on Qt's main thread.
    /// </summary>
    public async Task<string> TestAsync()
    {
        // On the UI thread
        await Task.Run(() =>
        {
            // On the background thread
        });
        // On the UI thread
        return "async result!"
    }
    
    /// <summary>
    /// .NET can activate signals to send notifications to Qml.
    /// </summary>
    public void ActivateCustomSignal(string message)
    {
        this.ActivateSignal("customSignal", message)
    }
}

using (var app = new QGuiApplication(r))
{
    using (var engine = new QQmlApplicationEngine())
    {
        // Register our new type to be used in Qml
        QQmlApplicationEngine.RegisterType<QmlType>("test", 1, 1);
        engine.loadFile("main.qml");
        return app.exec();
    }
}