什么是“$”标志而在C＃6.0？ [英] What does '$' sign do in C# 6.0?

问题描述

在MVC 6源代码中，我看到了字符串以$领先的迹象一些代码行。

In MVC 6 source code I saw some code lines that has strings leading with $ signs.

正如我以前从未看到它，我认为这是在C＃中新6.0。我不确定。 （我希望我是对的，否则我从未进过它，我会感到震惊。

As I never saw it before, I think it is new in C# 6.0. I'm not sure. (I hope I'm right, otherwise I'd be shocked as I never crossed it before.

这是这样的：

var path = $"'{pathRelative}'";

推荐答案

你是正确的，这是一个新的C＃6功能。

You're correct, this is a new C# 6 feature.

$ 字符串之前签署允许串插，编译器将专门解析字符串，大括号内的任何表达式将被计算并插入到位字符串。

The $ sign before a string enables string interpolation. The compiler will parse the string specially, and any expressions inside curly braces will be evaluated and inserted into the string in place.

在将其转换为同样的事情，因为这罩：

Under the hood it converts to the same thing as this:

var path = string.Format("'{0}'", pathRelative);

让我们看看IL这个片断：

Let's look at the IL for this snippet:

var test = "1";
var val1 = $"{test}";
var val2 = string.Format("{0}", test);

这编译为：

// var test = "1";
IL_0001: ldstr "1"
IL_0006: stloc.0

// var val1 = $"{test}";
IL_0007: ldstr "{0}"
IL_000c: ldloc.0
IL_000d: call string [mscorlib]System.String::Format(string, object)
IL_0012: stloc.1

// var val2 = string.Format("{0}", test);
IL_0013: ldstr "{0}"
IL_0018: ldloc.0
IL_0019: call string [mscorlib]System.String::Format(string, object)
IL_001e: stloc.2

于是两人都是在编译的应用程序是相同的。

So the two are identical in the compiled application.

C＃的串插语法的说明：不幸的是，水被搅浑，现在就串插，因为原来的C＃6预览过的那得到了很多的关注博客早早就不同的语法 。你还是会看到很多参考使用字符串插值反斜杠，但这已不再是语法上有效。

A note on the C# string interpolation syntax: Unfortunately the waters are muddied right now on string interpolation because the original C# 6 preview had a different syntax that got a lot of attention on blogs early on. You'll still see a lot of references to using backslashes for string interpolation, but this is no longer syntactically valid.

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