什么开销与在运行时的扩展方法有关？ （。净） [英] What overhead is associated with an extension method at runtime? (.NET)

问题描述

  

可能重复：
  扩展方法效果

在一个数据处理的应用程序即结合的CPU和/或存储器的访问，是一个行扩展方法noticable的开销？它比普通的函数调用任何更高，或者是它只是一个编译器/ IDE抽象？例如，将下面的函数是不明智的，如果它被称为几向上千倍第二：

 公共静态无效WriteElementString（这XmlTextWriter的作家，字符串名称，int数据）
{
    writer.WriteElementString（姓名，data.ToString（））;
}
 

解决方案

有没有开销。这只是调用不同的语法的静态方法。产生的IL只是一个普通的电话。

在换言之，开销为您的扩展方法是完全相同

  writer.WriteElementString（名称，数据）;
 

，如果你只是叫

  XmlWriterExtensions.WriteElementString（作家，名，数据）;
 

...因为生成的IL将完全相同。

在性能方面，向上几千次，第二次是的没有的。开销具有堆一层额外的保护将是完全无关紧要在这一水平......即使该方法不内联，我认为这是非常有可能在这种情况下。

然而，业绩的正常规则：它的所有猜测，直到你已经测量。或者至少，在实际的在这种情况下，冲击最大的是猜测;在扩展方法只是普通的方法，在编译器语法糖是不是猜测。

Possible Duplicate:
Extension Method Performance

In a data crunching application that is CPU and/or memory access bound, is the overhead of a one line extension method noticable? Is it any higher than a normal function call, or is it simply a compiler/IDE abstraction? For instance, would the following function be ill advised if it was being called upwards of several thousand times a second:

public static void WriteElementString(this XmlTextWriter writer, string name, int data)
{
    writer.WriteElementString(name, data.ToString());
}

解决方案

There's no overhead. It's just a static method called with different syntax. The IL generated is just a normal call.

In other words, the overhead for your extension method is exactly the same for

writer.WriteElementString(name, data);

as if you just called

XmlWriterExtensions.WriteElementString(writer, name, data);

... because the generated IL will be exactly the same.

In terms of performance, "upwards of several thousand times a second" is nothing. The overhead for having an extra level of stack will be utterly insignificant at that level... even if the method isn't inlined, which I believe it's very likely to be in this case.

However, the normal rule of performance applies: it's all guesswork until you've measured. Or at least, the actual hit in this case is guesswork; the "extension methods are just normal methods with syntactic sugar in the compiler" isn't guesswork.

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