C# Delegate.CreateDelegate vs DynamicMethod vs Expression
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Delegate.CreateDelegate vs DynamicMethod vs Expression
提问by jsw
Questions about Making reflection fly and exploring delegates...
关于使反射飞行和探索代表的问题......
If I need to create delegates Func<T, TResult>to methods on dynamically loaded types I could potentially use (1) Delegate.CreateDelegate(2) DynamicMethod(3) Expressiontrees.
如果我需要为Func<T, TResult>动态加载的类型的方法创建委托，我可能会使用 (1) Delegate.CreateDelegate(2) DynamicMethod(3)Expression树。
Lets say the set of dynamically loaded types/methods are reflected once at application startup via config and used throughout the lifetime of the app (start-up performance is not an issue and neither is memory), the delegates are cached and dispatched to in a strongly-typed way. These delegates are hot paths accessed concurrently.
假设动态加载的类型/方法集在应用程序启动时通过配置反映一次，并在应用程序的整个生命周期中使用（启动性能不是问题，内存也不是问题），委托被缓存并分派到强类型方式。这些委托是并发访问的热路径。
Which dynamic binding method would you prefer and why?
您更喜欢哪种动态绑定方法，为什么？
采纳答案by Jon Skeet
If they're actually existing methods which you have a MethodInfofor, and they have the right signatures, then I'd say Delegate.CreateDelegateis the right way to go - it does exactly what you want, with no fuss. I'd use DynamicMethodor expression trees if I needed to build a delegate to execute some logic which wasn't already captured in a method.
如果它们实际上是您拥有的现有方法MethodInfo，并且它们具有正确的签名，那么我会说这Delegate.CreateDelegate是正确的方法 - 它完全符合您的要求，没有大惊小怪。DynamicMethod如果我需要构建一个委托来执行一些尚未在方法中捕获的逻辑，我会使用或 表达式树。
Expression trees are (IMO, and I haven't used DynamicMethodin anger) slightly easier to use than DynamicMethod, but they're more restricted - basically they can only represent a single expression (which could call another method, of course). DynamicMethodgives you lots of flexibility, but you need to understand IL reasonably well.
表达式树（IMO，我没有DynamicMethod在愤怒中使用过）比 更容易使用DynamicMethod，但它们更受限制 - 基本上它们只能表示单个表达式（当然可以调用另一种方法）。DynamicMethod为您提供了很大的灵活性，但您需要相当好地理解 IL。
Does that help?
这有帮助吗？
回答by flq
Via Ayende's blog I got this interesting link which shows off the kind of things you can do with Dynamic Methods. As an example it is quite understandable:
Accelerating Enum-Based Dictionaries with Generic EnumComparer
通过 Ayende 的博客，我得到了这个有趣的链接，它展示了使用动态方法可以做的事情。举个例子，这是很容易理解的：
使用通用 EnumComparer 加速基于枚举的字典
Update
更新
One should note that in the world of WinRT, Reflection.Emitis unavailable - some information can be found here
应该注意的是，在 WinRT 的世界中，Reflection.Emit是不可用的 - 可以在此处找到一些信息
