C# 基础知识 protected 关键字

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
    public class A
    {
        protected int x = 123;
        internal protected int y = 123;
        void Test()
        {
            A a = new A();
            B b = new B();
            //a.x //ok
            //b.x //ok
            //a.y //ok
            //b.y //ok
        }
    }
    public class B : A
    {
        void Test()
        {
            A a = new A();
            B b = new B();
 
            //base.x ok
            //base.y ok
            //a.x = 10; erro
            //b.x = 10; //ok
            //a.y; ok
            //b.y; ok
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            A a = new A();
            B b = new B();
            //a.x = 10; erro
            //b.x = 10; erro
            //a.y; ok
            //b.y; ok
        }
    }
}