Hi, Im making a factory method that returns new instances of my objects. I would like to prevent anyone using my code from using a public constructor on my objects. Is there any way of doing this?

How is this typically accomplished:

public abstract class CarFactory
{
  public abstract ICar CreateSUV();
}

public class MercedesFactory : CarFactory
{
  public override ICar CreateSUV()
  {
    return new Mercedes4WD();
  }
}

I then would like to limit/prevent the other developers (including me in a few months) from making an instance of Mercedes4WD. But make them call my factory method. How to?