C＃正则表达式替换和* [英] C# Regex Replace and *

问题描述

我是一个Perl程序员做了一些的C＃。面对关于零或更多的断言与Regex.Replace一个奇怪的问题，*。

I'm a perl programmer doing a bit of C#. Facing an odd issue with Regex.Replace in regard to the zero-or-more assertion, *.

说我想用一个字母来代替零个或多个字母。在Perl中，我能做到这一点：

Say I wanted to replace zero or more letters with a single letter. In perl, I could do this:

my $s = "A";
$s =~ s/\w*/B/;
print $s;
$s now = "B"

但是，如果我尝试做在C＃中相同，像这样的：

But if I try and do the same in C#, like this:

string s = Regex.Replace("A", @"\w*", "B");
s now = "BB"

该文档不说的*字符不承认替换模式中的元字符

The docs do say "The * character is not recognized as a metacharacter within a replacement pattern"

为什么呢？而且没有任何变通，如果你想有点您正则表达式来啜了一些遗留下来的字符串，可能不存在（如。*？在终点）

Why? And is there any work around if you want a bit of your regex to slurp up some left over string which may not be there (like ".*?" on the end)

（这是一个愚蠢的例子，但你明白了吧）

(this is a silly example, but you get the point)

推荐答案

与启动模式^和$结束它你的问题就解决了。

Start your pattern with ^ and end it with $ and your problem is solved.

string s = Regex.Replace("AAAA", @"^\w*$", "B");
Console.Write(s);

另外 - 你可以停在0与 + 运营商，而不是 * 运营商：

Alternatively - you can stop matching on 0 length strings with the + operator instead of the * operator:

string s = Regex.Replace("AAAA", @"\w+", "B");
Console.Write(s);

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