Optional validation rule in FluentValidation

I have got two different models which extend an basemodel.

public class basemodel 
{
   public string prename;
   public string surname;
}

public class modelA : basemodel 
{
   public string street;
   public int gender; //0 = m / 1 = f
}

public class modelB : basemodel 
{
   public string street; 
}

Now I wanna validate them in my HTTP PUT controller. The controller decides between the modelA or modelB depending on the role a user has (admin can see modelA and user can see modelB).

public ActionResult Put(MyDto myDto)
{
   if (validationSrv.IsValid(myDto, ruleSetNames: "Edit", propertyNames: null))
   {
       session.Merge(myDto);
       session.Flush();
       session.Evict(myDto);
   } //else xyz
}

My actual validator looks like this.

public MyValidator() : AbstractValidator<basemodel>
{
   RuleSet("Edit", () =>
   {
       editBaseValidation();
   });
}

private void editBaseValidation()
{
   RuleFor(a => a.prename)
        .NotEmpty()
        .Length(5, 50);

   RuleFor(a => a.surname)
        .NotEmpty()
        .Length(5, 50);

   //say this is optional!
   RuleFor(a => a.street)
        .NotEmpty()

   //say this is optional!
   RuleFor(a => a.gender)
        .NotEmpty()
}

Now my question. Is there a way to say my validator that some attributes like street or gender are optional depending on the models used? So I can use only the validator for the basemodel and the validator decides which attribures to validate or not.

Thanks in advance :-)