为什么公共类不能从不太明显的类中继承？

Question

可能重复:
C#:为什么我的公共类不能扩展内部类？

如果以前曾问过这个问题,我道歉.我有点搜索,无法找到它.

我只是好奇这个设计背后的理由是什么.显然,我理解基类型的私有/内部成员不能,也不应该通过派生的公共类型公开.但我天真的想法似乎是,"隐藏"的部分可以很容易地隐藏起来,而一些基本功能仍然是共享的,并且新的界面是公开的.

我正在考虑这些方面的事情:

大会X.

internal class InternalClass
{
    protected virtual void DoSomethingProtected()
    {
        // Let's say this method provides some useful functionality.
        // Its visibility is quite limited (only to derived types in
        // the same assembly), but at least it's there.
    }
}

public class PublicClass : InternalClass
{
    public void DoSomethingPublic()
    {
        // Now let's say this method is useful enough that this type
        // should be public. What's keeping us from leveraging the
        // base functionality laid out in InternalClass's implementation,
        // without exposing anything that shouldn't be exposed?
    }
}

大会Y.

public class OtherPublicClass : PublicClass
{
    // It seems (again, to my naive mind) that this could work. This class
    // simply wouldn't be able to "see" any of the methods of InternalClass
    // from AssemblyX directly. But it could still access the public and
    // protected members of PublicClass that weren't inherited from
    // InternalClass. Does this make sense? What am I missing?
}

Answer 1

当一个类从基类继承时，基类成员就成为继承类的一部分。为了维持这个概念，基类的可见性范围必须等于或优于继承类。