Inheritance : does not contain a definition for and no extension method accepting a first argument

Question

abstract class Parent
{
        protected string attrParent;

        public AttrParent { get; protected set }

        public Parent(string sParent)
        {
                  


        

Answer 1

The moment you assign Child instance to variable typed as Parent you can only access members declared on Parent.

You'd have to downcast it back to Child to access Child-only members:

Parent p = new Child();

Child c = (Child)p;
c.AttrChild = "hello";

That cast might fail at runtime, because there might be a different class that inherits Parent.