Conditionally block method override

I have an application where the parent object has a method to perform validations and every child overrides the method to perform extra validations. Something like:

class Parent {
    virtual void DoValidations (Delegate addErrorMessage) {
        //do some validations
    }
}

class Child : Parent {
    override void DoValidations (Delegate addErrorMessage) {
         base.DoValidations(addErrorMessage); //the parent method is always called
         //do some extra validations
   }
}

I added a new "IsDisabled" property that when true the method will not perform any validations.

class Parent {
    boolean IsDisabled;

    virtual void DoValidations (Delegate addErrorMessage) {
        if (IsDisabled)
            return;
        //do some validations
    }
}

I also want that for every child, if the "IsDisabled" property is true, the extra verifications aren't performed. What is the better pattern to use here?