是否有可能重写非虚方法？ [英] Is it possible to override a non-virtual method?

问题描述

有没有什么办法来覆盖非虚方法？或东西，让类似的结果（不是创建一个新方法等来调用所需的方法）？

Is there any way to override a non-virtual method? or something that gives similar results (other than creating a new method to call the desired method)?

我想覆盖从 Microsoft.Xna.Framework.Graphics.GraphicsDevice 的方法在考虑单元测试。

I would like to override a method from Microsoft.Xna.Framework.Graphics.GraphicsDevice with unit testing in mind.

推荐答案

没有，你不能忽略非虚方法。你能做的最接近的事是隐藏通过创建一个新方法同名的方法，但这是不可取的，因为它打破了良好的设计原则。

No, you cannot override a non-virtual method. The closest thing you can do is hide the method by creating a new method with the same name but this is not advisable as it breaks good design principles.

但是，即使隐藏的方法不会给你的执行时间的方法态分派调用，例如将一个真实的虚拟方法调用。考虑这个例子：

But even hiding a method won't give you execution time polymorphic dispatch of method calls like a true virtual method call would. Consider this example:

using System;

class Example
{
    static void Main()
    {
        Foo f = new Foo();
        f.M();

        Foo b = new Bar();
        b.M();
    }
}

class Foo
{
    public void M()
    {
        Console.WriteLine("Foo.M");
    }
}

class Bar : Foo
{
    public new void M()
    {
        Console.WriteLine("Bar.M");
    }
}

在这个例子中两个呼叫到 M 方法打印 Foo.M 。正如你所看到的这种做法确实让你有一个方法，一个新的实现，只要参照该对象是正确的派生类型，但隐藏的基础方法的确实的突破多态性。

In this example both calls to the M method print Foo.M. As you can see this approach does allow you to have a new implementation for a method as long as the reference to that object is of the correct derived type but hiding a base method does break polymorphism.

我会建议你不要躲在这种方式的基础方法。

I would recommend that you do not hide base methods in this manner.

我倾向于与那些谁赞成C＃的默认行为方法都是非虚默认情况下（而不是Java的）到另一边。我会再进一步​​说，类应该也被默认密封。继承是很难设计的正确和事实，那就是未标记是虚拟的方法表明，该方法从未用于该方法的作者被覆盖。

I tend to side with those who favor C#'s default behavior that methods are non-virtual by default (as opposed to Java). I would go even further and say that classes should also be sealed by default. Inheritance is hard to design for properly and the fact that there is a method that is not marked to be virtual indicates that the author of that method never intended for the method to be overridden.

编辑：执行时间多态分派

我的意思是，在执行时，当你调用虚方法发生的默认行为。比方说，例如，在我的previous code例如，而不是定义一个非虚方法，我做实际上定义了一个虚拟的方法和一个真正的重写的方法为好。

What I mean by this is the default behavior that happens at execution time when you call virtual methods. Let's say for example that in my previous code example, rather than defining a non-virtual method, I did in fact define a virtual method and a true overridden method as well.

如果我是在这种情况下调用 b.Foo 时，CLR会正确地确定对象的类型的 B 的参考点为酒吧和将派调用 M 恰如其分。

If I were to call b.Foo in that case, the CLR would correctly determine the type of object that the b reference points to as Bar and would dispatch the call to M appropriately.

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