public partial MyUserControl()
{
    InitializeComponent();
    Model.Initialize(DI.Resolve<IMyService>());
    Loaded += () => { Model.OnLoaded(); };
    Unloaded += () => { Model.OnUnloaded(); };
}

public class MyViewModel
{
    private bool _isLoaded = false;
    private IMyService _myService;

    public MyViewModel() {
        // TODO: Add your constructor code here
        // The ctor is always called, initialize view model so that it also works in designer
    }

    public void InitializeIMyService myService) {
        _myService = myService;
        // TODO: Add your initialization code here
        // This method is only called when the application is running
    }

    public void OnLoaded()  {
        if (!_isLoaded)  {
            // TODO: Add your loaded code here
            _isLoaded = true;
        }
    }

    public void OnUnloaded()  {
        if (_isLoaded) {
            // TODO: Add your cleanup/unloaded code here
            _isLoaded = false;
        }
    }
    ...