public class Widget : Gear
{
    public override string Spin()
    {
        return "crunch";
    }
}

public class Gear
{
    public virtual string Spin()
    {
        return "whirr";
    }
}

var widget = new Widget();
for (var i = 0; i < 1000; i++)
{
   Console.WriteLine(widget.Spin());
}

> ...
> crunch
> crunch
> crunch
> whirr
> crunch
> ...

class Gear {
  public virtual string Spin() {
    return "whirr";
  }
}