排除以特定字符开头的正则表达式匹配 [英] Excluding regex matches that are preceded by a certain character

问题描述

我有以下内容:

        Regex urlRx = new Regex(@"((https?|ftp|file)\://|www.)[A-Za-z0-9\.\-]+(/[A-Za-z0-9\?\#\&\=;\+!'\(\)\*\-\._~%]*)*", RegexOptions.IgnoreCase);

这匹配所有URL，但是我想排除那些以"或'字符开头的URL.我一直在尝试使用其他URL来实现.解决方案(正则表达式排除[除非在\ 之前)能够通过它.

This matches all URLs, but I'd like to exclude those that are preceded by the characters " or '. I've been trying to achieve this using other solutions (Regex to exclude [ unless preceded by \) but haven't been able to get it to pass.

如果我有这个:

The brown fox www.google.com

我应该得到一场比赛.但是如果我有这个:

I should get a match. But if I have this:

The brown fox <a href="www.google.com">boo</a>

由于"，我不应该得到比赛.如何实现?

I should not get a match, because of the ". How can this be achieved?

推荐答案

您需要后面的负向外观:用(?<！['])前缀正则表达式代码>.

You need a negative lookbehind: Prefix your regular expression by (?<!["']).

说明:

• (?<！...)的意思是:直接在当前位置之前的东西不能与 ... 匹配./li>
• ['] 只是一个字符组，其中包含您要排除的两个字符.

• (?<!...) means: The stuff directly preceding the current position must not match ....
• ["'] is simply a character group containing the two characters you want to exclude.

注意:在 @"..." 字符串中，通过将双qoutes加倍来转义它们，因此您的代码将显示为:

Note: Inside @"..." strings, double qoutes are escaped by doubling them, so your code will read:

Regex urlRx = new Regex(@"(?<![""'])((https?|ftp|file)...

在VB中:

Dim urlRx As New Regex("(?<![""'])((https?|ftp|file)...

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