从覆盖的方法阻止C＃子 [英] Preventing a C# subclass from overwriting a method

问题描述

说我有一个名为父的抽象父类实现了一个名为DISPLAYTITLE的方法。我想这个方法是继承父每个子类相同的 - 如果一个子类，试图实现自己的DISPLAYTITLE的方法，我想编译错误。我如何在C＃中做到这一点。我相信，在Java中，我只是标记方法，最终的，但我似乎无法找到在C＃中的替代品。我一直在封闭和覆盖瞎搞，但我不能得到我要找的行为。

例如，在此代码：

 使用系统; 
 
命名ConsoleApplication1 
 {
级父
 {
公共无效DISPLAYTITLE（）{Console.WriteLine（父的标题）; } 
} 
 
类ChildSubclass：家长
 {
公共无效DISPLAYTITLE（）{Console.WriteLine（孩子自己的标题的执行情况）; 
} 
 
静态无效的主要（字串[] args）
 {
 ChildSubclass myChild =新ChildSubclass（）; 
 myChild.DisplayTitle（）; 
到Console.ReadLine（）; 
} 
} 
} 
  

我想收到编译错误说，ChildSubClass无法覆盖DISPLAYTITLE。目前，我得到一个警告 - 但似乎这是一件我应该可以做的，我不知道正确的属性标记方法

解决方案

如何在C＃中做到这一点。我相信，在Java中，我只是标记方法，最终的，但我似乎无法找到在C＃中的替代品。

大致相当于为密封在C＃中，但你通常只需要它的虚方法 - 和你的 DISPLAYTITLE 方法不是虚拟的。

要注意这一点很重要 ChildSubclass 的不是的覆盖 DISPLAYTITLE - 它的隐藏的它。其中只使用引用父任何代码不会最终调用该实现。

请注意，与代码原样，你应该得到一个编译时警告，提醒您对新修改添加到方法 ChildSubclass

 公开新无效DISPLAYTITLE（）{...} 
  

您不能的停止的隐藏，从现有的方法，除了通过密封类本身来防止派生类的创建完全派生类...但不直接使用派生类型不会在意。

呼叫者

什么是你的真正的关注吗？ ？意外误用或故意的问题。

编辑：请注意，您的示例代码警告会是这样的：

  test.cs中（12,19）​​：警告CS0108：
'ConsoleApplication1.ChildSubclass.DisplayTitle（）隐藏继承
会员'ConsoleApplication1.Parent.DisplayTitle（ ）。使用new关键字
如果隐藏之意。 
  

我建议你把警告变成错误，然后它很难忽略它们：）

Say I have an abstract parent class called "Parent" that implements a method called "DisplayTitle". I want this method to be the same for each subclass that inherits "Parent" - I would like a compile error if a subclass attempts to implement their own "DisplayTitle" method. How can I accomplish this in C#. I believe in Java, I'd just mark the method as "final", but I can't seem to find an alternative in C#. I've been messing around with "sealed" and "override", but I can't get the behavior that I'm looking for.

For example, in this code:

using System;

namespace ConsoleApplication1
{
  class Parent
  {
      public void DisplayTitle() { Console.WriteLine("Parent's Title"); }
  }

  class ChildSubclass : Parent
  {
      public void DisplayTitle() { Console.WriteLine("Child's Own Implementation of Title"); 
  }

    static void Main(string[] args)
    {
        ChildSubclass myChild = new ChildSubclass();
        myChild.DisplayTitle();
        Console.ReadLine();
    }
  }
}

I'd like to receive a compile error saying that the "ChildSubClass" can't override "DisplayTitle". I currently get a warning - but it seems like this is something that I should be able to do and I don't know the proper attributes to label the method.

解决方案

How can I accomplish this in C#. I believe in Java, I'd just mark the method as "final", but I can't seem to find an alternative in C#.

The rough equivalent is sealed in C#, but you normally only need it for virtual methods - and your DisplayTitle method isn't virtual.

It's important to note that ChildSubclass isn't overriding DisplayTitle - it's hiding it. Any code which only uses references to Parent won't end up calling that implementation.

Note that with the code as-is, you should get a compile-time warning advising you to add the new modifier to the method in ChildSubclass:

public new void DisplayTitle() { ... }

You can't stop derived classes from hiding existing methods, other than by sealing the class itself to prevent the creation of a derived class entirely... but callers which don't use the derived type directly won't care.

What's your real concern here? Accidental misuse, or deliberate problems?

EDIT: Note that the warning for your sample code would be something like:

Test.cs(12,19): warning CS0108:
        'ConsoleApplication1.ChildSubclass.DisplayTitle()' hides inherited
        member 'ConsoleApplication1.Parent.DisplayTitle()'. Use the new keyword
        if hiding was intended.

I suggest you turn warnings into errors, and then it's harder to ignore them :)

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