public class Base { protected Base() { } } public class Derived : Base { public static void Main() { Base obj = new Base(); /* error CS1540: Cannot access protected member 'Base.Base()' via a qualifier of type 'Base'; the qualifier must be of type 'Derived' (or derived from it) */ } } Remarks: as of 2.0, derived class can access a protected instance constructor of a base class only in a constructor-initializer.