C#关键字中的访问修饰符protected

https://msdn.microsoft.com/zh-cn/library/bcd5672a.aspx

官方的说法The protected keyword is a member access modifier. A protected member is accessible within its class and by derived class instances.

protected关键字是一个成员访问修饰符。一个protected的成员，一个protected成员，在其所在的类中，可由其派生类的实例访问。

可访问性级别的介绍：

https://msdn.microsoft.com/zh-cn/library/ba0a1yw2.aspx

protected ：Access is limited to the containing class or types derived from the containing class.

protected关键字：只能由包含的类进行访问，或者从包含该成员的类所派生的类进行访问。

疑惑的地方：错误观点我本以为只要是派生类的实例，就可以访问受保护的成员。

http://blogs.msdn.com/b/ericlippert/archive/2005/11/09/why-can-t-i-access-a-protected-member-from-a-derived-class.aspx

class Ungulate {

  protected virtual void Eat() { /* whatever */ }
}

class Zebra : Ungulate {
  protected override void Eat() { /* whatever */ }
}

class Giraffe : Ungulate {
  public static void FeedThem() {
    Giraffe g1 = new Giraffe();
    Ungulate g2 = new Zebra();
    g1.Eat(); // fine
    g2.Eat(); // compile-time error "Cannot access protected member"
  }
}

We can call Ungulate.Eat legally from Giraffe,

but we can‘t call the protected method Zebra.Eat from anything except Zebra or a subclass of Zebra.

Since the compiler cannot determine from the static analysis that we are not in this illegal situation, it must flag it as being illegal.

C#关键字中的访问修饰符protected

原文：http://www.cnblogs.com/chucklu/p/4481642.html