c# - Protected method access from derived class -

i have protected method in base class :

public class baseclass {   protected virtual void foo(){} }     

the method overrided 1 of derived classes:

public class derived1 : baseclass {    protected override void foo()     {      //some code...     } }     

another derived class has instance of first derived class.
when try access foo method (existing in base class, mentiond) error :

 public class derivedclass2 : baseclass     {      baseclass instance = new derivedclass1();      instance.foo(); // here error     } 

the error get:

error cs1540: cannot access protected member 'baseclass.foo' via qualifier of type 'baseclass';    qualifier must of type 'derivedclass2' (or derived it) 

i understand protected members should not give value other instance, instance derived same type,
there way not modify method public?

you can make foo method declaration protected internal....

public class baseclass {   protected internal virtual void foo(){} }   public class derived1 : baseclass {    protected internal override void foo()     {      //some code...     } } 

here "protected internal" means member visible class inheriting base class, whether it's in same assembly or not. member visible via object declared of type anywhere in same assembly.