[FxCop.设计规则]1. 抽象类不应该拥有构造函数

1. 抽象类不应该拥有构造函数原文引用：Abstract types should not have constructors

TypeName:

AbstractTypesShouldNotHaveConstructors

CheckId:

CA1012

Category:

Microsoft.Design

Message Level:

CriticalWarning

Certainty:

95%

Breaking Change:

NonBreaking

Cause: A public type is abstract and has a public constructor.

Rule Description

Constructors on abstract types can only be called by derived types. Because public constructors create instances of a type, and you cannot create instances of an abstract type, an abstract type with a public constructor is incorrectly designed.

How to Fix Violations

To fix a violation of this rule, either make the constructor protected, or do not declare the type as abstract.

When to Exclude Messages

Do not exclude a message from this rule.

Example Code

The following example contains an abstract type that violates this rule, and an abstract type that is correctly implemented.

[C#]

using System;

namespace DesignLibrary

{

public abstract class BadAbstractClassWithConstructor

{

// Violates rule: AbstractTypesShouldNotHaveConstructors.

public BadAbstractClassWithConstructor()

{

// Add constructor logic here.

}

}

public abstract class GoodAbstractClassWithConstructor

{

protected GoodAbstractClassWithConstructor()

{

// Add constructor logic here.

}

}

}

引起的原因：一个公共抽象类型拥有一个公共的构造函数

描述：构造函数被用来建立一个对象实例，但是你不能建立一个抽象类型的实例，抽象类型的构造函数就仅仅能够被它的继承类型使用。因此，为一个抽象类构造公共构造函数是一个错误的设计。

修复：如果需要修复这个问题，可以声明这个构造函数为保护型，或者，声明这个类型不是一个抽象类型。