我有一个特定的正则表达式我试图用一些难度。我在寻找一个字符串的每个实例（对于我而言，我会说这是 MyString中的）的文件，除非它是一个标签，如：

I'm having some difficulty with a specific Regex I'm trying to use. I'm searching for every occurrence of a string (for my purposes, I'll say it's "mystring") in a document, EXCEPT where it's in a tag, e.g.

<a href="_mystring_">

应该不匹配，但

should not match, but

<a href="someotherstring">_mystring_</a>

应该匹配，因为它不是一个标签内（里面的意思里的＆lt;和>标记）。我使用.NET的正则表达式功能这个问题，以及

Should match, since it's not inside a tag (inside meaning "inside the < and > markers") I'm using .NET's regex functions for this as well.

推荐答案

这应该做到这一点：

(?<!<[^>]*)_mystring_

它使用一个负的外观背后，以检查匹配的字符串不具有＆LT;之前它没有相应的>

It uses a negative look behind to check that the matched string does not have a < before it without a corresponding >