C# 内联函数参数和临时变量
我想知道 C# 中的以下情况。
有时函数名称可能非常长且冗长。我在工作中使用 Microsoft 的 MVC 3 框架作为网站，这是一个示例函数：
[ImportModelStateFromTempData]
[BreadCrumb("New Event")]
public ActionResult New()
{
var @event = _dbContext.EventRepository.CreateNewEvent();
return View("New",
EventViewModel.FromEventDomainModel(@event));
}
可以在不使用临时变量 @event 的情况下重写此代码，如下所示：
[ImportModelStateFromTempData]
[BreadCrumb("New Event")]
public ActionResult New()
{
return View("New",
EventViewModel.FromEventDomainModel(_dbContext.EventRepository.CreateNewEvent()));
}
第一个示例显然更清晰，但从纯粹的好奇心角度来看/性能角度，哪个比另一个更快？特别是考虑到缓存值@event仅使用一次。
在 C++ 中，我记得发现 @event 的局部变量声明（如果这是 C++）将存储在 New() 的堆栈帧中，并且生成的程序集会比直接内联参数稍微慢一些（与将其存储在临时文件中）。
C# 编译器对于这种情况是否更聪明？我可以自由使用临时的而不需要考虑相同的性能吗？
我知道预优化是邪恶的，我绝对不应该担心这种事情，但我对此很好奇。我什至不确定我该去哪里查找有关此问题的更多信息，因为标题是我描述问题的最佳方式。那么你觉得 Stack Overflow 怎么样？
I was wondering about the following situation in C#.
Sometimes function names can be quite long, and verbose. I'm using Microsoft's MVC 3 framework for a website at work, Here's an example function:
[ImportModelStateFromTempData]
[BreadCrumb("New Event")]
public ActionResult New()
{
var @event = _dbContext.EventRepository.CreateNewEvent();
return View("New",
EventViewModel.FromEventDomainModel(@event));
}
This code could be rewritten without use of the temporary variables @event, like so:
[ImportModelStateFromTempData]
[BreadCrumb("New Event")]
public ActionResult New()
{
return View("New",
EventViewModel.FromEventDomainModel(_dbContext.EventRepository.CreateNewEvent()));
}
The first example is obviously more clear, but from a pure curiosity perspective/performance perspective, is either faster than the other? Especially considering that the cached value @event is only being used once.
In C++ I remember finding out that the local variable declaration of @event (if this were C++) would be stored in New()'s stack frame, and the assembly generated would be SLIGHTLY slower than directly in-lining the argument (as opposed to storing it in a temporary).
Is the C# compiler smarter about this situation? Am I free to use temporary's without the same performance considerations?
I understand that pre-optimization is evil, and I absolutely should not be worried about this kind of this, but I am curious about this. I'm not even sure about where I would go looking up more information about this, as the title was the best way I could describe my question. So what do you think Stack Overflow?
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这些产生的 IL 将是等效的。如果您想向自己证明这一点，请尝试编译两者并使用 Ildasm http://msdn.microsoft.com/en-us/library/f7dy01k1(v=vs.80).aspx
The IL produced by these will be equivalent. If you want to prove it to yourself, try compiling both and looking at the resulting IL with Ildasm http://msdn.microsoft.com/en-us/library/f7dy01k1(v=vs.80).aspx
临时变量是好的。
调试时，可以检查函数的结果。
延迟（如果有）以纳秒或皮秒为单位。
保养为王。
Temporary variables are good.
When you are debugging, you can check the results of functions.
The delay, if there is one, is in nano or pico seconds.
Maintenance is king.