Question

I’m porting some Java code to C#, and I ran into this idiom used to copy objects:

class Base
{
    int x;
    public Base(int x) { this.x = x; }
    protected Base(Base other) { x = other.x; }
}

class Derived : Base
{
    Base foo;
    public Derived(Derived other)
        : base(other)
    {
        foo = new Base(other.foo); // Error CS1540
    }
}

Error CS1540 being:

Cannot access protected member ‘Base.Base(Base)’ via a qualifier of type ‘Base’; the qualifier must be of type ‘Derived’ (or derived from it)

I understand the purpose of this error: it prevents accessing protected members of sibling types. But Base.Base(Base) is obviously not going to be invoked on a sibling type! Is this simply not included in the spec, or am I missing some reason why this would not be safe?

EDIT: Gah, the idiom was new Base(other.foo) not new Base(other)

Answer 1

its not accessible you can check this post for details : Many Questions: Protected Constructors