Lambda被视为罗斯林的封闭代表 [英] Lambda treated as a closed delegate in Roslyn

问题描述

我很惊讶这两个委托（ fn1 和 fn2 ）之间会存在运行时差异： / p>

I was surprised that there would be any runtime difference between these two delegates (fn1 and fn2):

static int SomeStaticMethod(int x) { return x; }

// fn1.Target == null in this case
Func<int, int> fn1 = SomeStaticMethod;

// fn2.Target != null in this case
Func<int, int> fn2 = x => x;

但是显然第二个lambda被视为实例方法，因为它的 Target 属性为非null。在我切换到Visual Studio 2015之前，它的处理方式有所不同（在VS2012中，我很确定它被视为静态方法）。

But apparently the second lambda is treated like an instance method, because its Target property is non-null. And it was treated differently before I switched to Visual Studio 2015 (in VS2012, I am pretty sure it was treated as a static method).

没有闭包的lambda在C＃中被视为封闭的委托（即实例方法）？我以为可能是调试器添加了一些东西，但是它也发生在发行版中。

Is there a reason why a lambda with no closures is treated as a closed delegate (i.e. an instance method) in C#? I thought perhaps it's the debugger adding some stuff, but it also happens in release builds.

（澄清）

关键是，我有一个像这样的方法，它创建了一个通用委托来快速从枚举转换为整数（无装箱）：

The point is, I had a method like this which created a generic delegate for quickly converting from enums to ints (without boxing):

private static Func<int, TEnum> CreateIntToEnumDelegate()
{
    Func<int, int> lambda = x => x;
    return Delegate.CreateDelegate(typeof(Func<int, TEnum>), lambda.Method) 
        as Func<int, TEnum>;
}

在罗斯林不再有效了，因为实例 lambda与委托人签名不兼容。因此，我不得不使用 static 方法，没什么大不了的。

and it didn't work in Roslyn anymore, because the "instance" lambda became incompatible with the delegate signature. So I had to use a static method instead, no big deal.

但是让我担心的是，这在编译时是不可能发现的。 此线程描述了类似的问题，顺便说一句，现在我搜索了罗斯林代表 。

But what worries me is that this was impossible to catch during compile-time. This thread describes similar issues, btw, now that I searched for "Roslyn delegates".

推荐答案

这是 2014年对罗斯林进行的更改。确实很奇怪，但是实际上是为了改善性能 。 在新策略中，所有lambda都作为实例方法发出 -来自讨论在roslyn.codeplex.com （注意：无效链接）。

This was a change made to Roslyn in 2014. It is quite strange, but it was actually done to improve performance. "In the new strategy all lambdas are emitted as instance methods" - from the discussion at roslyn.codeplex.com (note: dead link).

这篇关于Lambda被视为罗斯林的封闭代表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！