是否可以在运行时向EXISTING类添加一个方法？为什么或者为什么不？ [英] Is it possible to add a method to an EXISTING class at runtime? why or why not?

问题描述

我想象这可能会使用Reflection.Emit，

I would imagine this might use Reflection.Emit,

但类似于SO的问题只能回答如何动态创建一个类/方法，而不是如何更新现有的类。

but a similar question on SO only answers how to create a class/method dynamically, not how to update an existing class.

同样的，在运行时可以删除方法/类吗？如果是这样，我想可以删除该类，并将其添加到旧方法加上新的方法。

In a similar vein, is it possible to delete methods / classes at runtime? If so, I suppose one could just delete the class, and add it back with its old methods plus the new one.

提前感谢。

PS我没有预期的用途，这只是一个好奇的问题。

P.S. I don't have an intended use for this, it is merely a matter of curiosity.

推荐答案

在常规的C＃/ .NET答案是一个简单的不。您可以做的最多的是写一个 DynamicMethod ，可以像这种类型的方法（访问私有字段等）行为，但它赢得了不要在API上 - 你只需要一个委托。

In regular C# / .NET, the answer is a simple "no". The most you can do is write a DynamicMethod which can behave like a method of that type (access to private fields etc), but it won't ever be on the API - you just end up with a delegate.

如果你使用动态，你可以做任何你想要的任何事情您可以使用 ExpandoObject 通过附加代理来代替方法，但是对于自定义动态类型，您可以执行大多数操作 - 但这只会影响使用动态 API的呼叫者。对于基本的 ExpandoObject 示例：

If you use dynamic, you can do pretty much anything you want. You can emulate that with ExpandoObject by attaching delegates in place of methods, but on a custom dynamic type you can do most anything - but this only impacts callers who use the dynamic API. For a basic ExpandoObject example:

dynamic obj = new ExpandoObject();
Func<int, int> func = x => 2*x;
obj.Foo = func;
int i = obj.Foo(123); // now you see it
obj.Foo = null; // now you don't

对于属性和事件（不是方法），您可以使用 System.ComponentModel 方法更改运行时显示的内容，但这只会影响通过 System.ComponentModel ，这主要表示：UI数据绑定。这就是 DataTable 表示列作为伪属性（暂时忘了打字数据集） -

For properties and events (not methods), you can use the System.ComponentModel approach to change what appears at runtime, but that only impacts callers who get access via System.ComponentModel, which means mainly: UI data-binding. This is how DataTable represents columns as pseudo-properties (forgetting about "typed datasets" for the moment - it works without those).

为了完整，我还应该提到扩展方法。那些更多的是一个编译器技巧，而不是一个运行时技巧 - 但是，您可以使用添加方法到现有类型 - 对于小的add值。

For completeness, I should also mention extension methods. Those are more a compiler trick, not a runtime trick - but kinda allow you to add methods to an existing type - for small values of "add".

ORMs等通常使用的最后一个技巧是动态子类，并在子类中提供附加功能。例如，覆盖属性以截取它们（延迟加载等）。

One final trick, commonly used by ORMs etc - is to dynamically subclass the type, and provide additional functionality in the subclass. For example, overriding properties to intercept them (lazy-loading, etc).

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