using System;

public class Program

{

    public static void Main()

    {

        var welcomePage = new WelcomePage();

        var welcomePageViewModelIsNull = welcomePage.GetViewModel() == null;

        Console.WriteLine("Is welcome page view model null? " + welcomePageViewModelIsNull);

        var bindingPage = new BindingPage();

        var bindingPageViewModelIsNull = bindingPage.GetViewModel() == null;

        Console.WriteLine("Is binding page view model null? " + bindingPageViewModelIsNull);

    }

    public class BindingPage : WizardPageBase

    {   

        public override ViewModelBase GetViewModel()

        {

           return new ViewModelBase();  

        }       

    }

    public class WelcomePage : WizardPageBase

    {

    }

    public abstract class WizardPageBase //: Page

    {

        public virtual ViewModelBase GetViewModel()

        {

            return null;

        }

    }

    public class ViewModelBase

    {

    }

}