为什么C＃允许没有抽象成员的抽象类？ [英] Why does C# allow abstract class with no abstract members?

问题描述

C＃的规范，节10.1.1.1 指出：

这是抽象类是允许的（但不是必需的
）包含抽象的
的成员。

An abstract class is permitted (but not required) to contain abstract members.

这让我可以创建类是这样的：

This allows me to create classes like this:

public abstract class A
{
    public void Main() 
    {
        // it's full of logic!
    }
}

甚至更好：

Or even better:

public abstract class A
{
    public virtual void Main() { }
}

public abstract class B : A
{
    public override sealed void Main()
    {
        // it's full of logic!
    }
}

这是一个真正的具体类;一心不能实例化它，它只是在目前为止的抽象。例如，如果我想在执行逻辑B.Main（）我必须首先获得B的情况下，这是不可能的。

This is really a concrete class; it's only abstract in so far as one can't instantiate it. For example, if I wanted to execute the logic in B.Main() I would have to first get an instance of B, which is impossible.

如果传承人实际上并没有提供实现，那么，为什么把它叫做抽象？

If inheritors don't actually have to provide implementation, then why call it abstract?

换句话说，为什么C＃允许只用混凝土构件的抽象类？

Put another way, why does C# allow an abstract class with only concrete members?

我要指出，我已经熟悉的抽象类型和成员的预期功能。

I should mention that I am already familiar with the intended functionality of abstract types and members.

推荐答案

也许一个很好的例子，是一种常见的基类，提供共享的特性，也许还有其他成员派生类，但并不代表一个具体的对象。例如：

Perhaps a good example is a common base class that provides shared properties and perhaps other members for derived classes, but does not represent a concrete object. For example:

public abstract class Pet
{
    public string Name{get;set;}
}

public class Dog : Pet
{
    public void Bark(){ ... }
}

所有宠物都有名字，但宠物本身是一个抽象的概念。宠物的实例必须是狗或一些其它种类的动物

All pets have names, but a pet itself is an abstract concept. An instance of a pet must be a dog or some other kind of animal.

这里的差别在于不是提供应被实现覆盖的方法，该基类声明所有的宠物都至少由名称属性。

The difference here is that instead of providing a method that should be overridden by implementors, the base class declares that all pets are composed of at least a Name property.

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