1. 抽象类不应该拥有构造函数
原文引用：
Abstract types should not have constructors
|
TypeName:
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AbstractTypesShouldNotHaveConstructors
---|---
CheckId:
|
CA1012
Category:
|
Microsoft.Design
Message Level:
|
CriticalWarning
Certainty:
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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。