Refactoring_to_improve_maintainability_and_blendability_using_IoC_part_2_04.cs

public abstract class ViewModelFactory<TViewModel, TDesignViewModel>
    where TViewModel : IViewModel
    where TDesignViewModel : TViewModel, new()
{
    public ViewModelFactory()
    {
    }

    public TViewModel ViewModel
    {
        get
        {
            TViewModel viewModel;
            bool designMode = DetectDesignMode();

            if (designMode)
            {
                // At design time instantiate design time version.
                // Populates mock data, dependencies don't have to be real.
                viewModel = new TDesignViewModel();
            }
            else
            {
                // Request IoC container to resolve view model & its deps.
                viewModel =
                    ApplicationHost.Current.Container.Resolve<TViewModel>();
            }

            viewModel.OnLocated();
            return viewModel;
        }
    }
}