c# - 为什么抽象类不能是密封的或静态的？

Question

为什么抽象类不能是sealed或者static的？

我也对这个问题感到困惑 Why declare static classes as sealed and abstract in C#? .

Answer 1

1. static 类不能标记为sealed，因为编译器默认将其设置为sealed。

   Static classes are sealed and therefore cannot be inherited.

2. static 类不能被标记为abstract，因为它毫无意义。当您希望所有派生类都实现相同的逻辑部分时，abstract 类很有意义。但是由于无法派生 static 类，因此其他类无法实现这些差距。

   They cannot inherit from any class except Object.

均引自 Static Classes and Static Class Members (C# Programming Guide) .

C# 规范对此更详细一些:

10.1.1.3 Static classes

A static class may not include a sealed or abstract modifier. Note, however, that since a static class cannot be instantiated or derived from, it behaves as if it was both sealed and abstract.

您可以阅读类被密封或抽象是什么意思:

An abstract class cannot be instantiated directly, and it is a compile-time error to use the new operator on an abstract class

The sealed modifier is used to prevent derivation from a class. A compile-time error occurs if a sealed class is specified as the base class of another class.

更新

关于您提到的查询中链接的一篇文章的词 ( Static Class Design )。它已经在该问题的已接受答案中说明。如果你仔细阅读，你会发现:

√ DO declare static classes as sealed, abstract, and add a private instance constructor if your programming language does not have built-in support for static classes.

.NET(C# 也是如此)确实内置了对静态类的支持，因此您不必(甚至不能)通过标记使您的类成为伪静态它既是密封的又是抽象的。