C#:覆盖父类的属性 [英] C#: override a property of the parent class

问题描述

我有一个继承自X509Certificate2的类.我希望NotAfter属性位于UTC而不是本地时间.我是C#的新手，我想知道下面的内容是最好的方法吗?

I have a class that inherits from X509Certificate2. I want the NotAfter property to be in UTC rather than local time. I'm pretty new to C# and was wondering if what I have below is the best way of doing it?

internal class Certificate : X509Certificate2
{
    public new DateTime NotAfter 
    {
        get { return base.NotAfter.ToUniversalTime(); }
    }

编辑 当我将其更改为:

public override DateTime NotAfter 
{
    get { return base.NotAfter.ToUniversalTime(); }
}

Resharper抱怨没有合适的属性可以覆盖"

Resharper complained that "There is not suitable property for override"

推荐答案

您在那里所做的是成员隐藏.如果您派生的类已将该属性标记为virtual，或从其基础(如果有)覆盖它，则可以使用override关键字:

What you have done there is member hiding. If the class you are deriving from has marked the property as virtual, or is overriding it from it's base (if it has one) you use the override keyword:

public override DateTime NotAfter

在基类已标记为virtual时可以使用成员隐藏，但是，如果有人将对您的类的引用转换为基类并访问该成员，他们将绕过您的new隐藏.使用override进行真正的继承时，不会发生此问题.

The member hiding can be used when the base class has marked it virtual, however if someone cast a reference of your class into the base class and accessed the member, they would bypass your new hiding. With true inheritance using override, this problem does not occur.

正如某人所指出的，此属性未标记为virtual:

As has been noted by someone, this property is not marked virtual:

http://msdn .microsoft.com/en-us/library/system.security.cryptography.x509certificates.x509certificate2.notafter.aspx

如果人们直接使用您的类，则隐藏成员可以使您解决此问题，但是当有人将您的类强制转换为基本类型时，他们将获得基本值:

Member hiding will allow you to get around this if people use your class directly, but the moment someone casts your class back to a base type, they get the base value:

class MyClass : Cert...

MyClass c = new MyClass();
DateTime foo = c.NotAfter; // Your newly specified property.

Cert cBase = (Cert)c;
foo = cBase.NotAfter; // Oops, base value.  Inheritance cures this, but only with virtual members.

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