[英]regex to exclude if preceded by string?
I haven't used regex much before but found something useful on the net that I'm using: 我以前没有使用过正则表达式,但是在网上发现了一些有用的东西:
private string ConvertUrlsToLinks(string msg)
{
string regex = @"((www\.|(http|https|ftp|news|file)+\:\/\/)[_.a-z0-9-]+\.[a-z0-9\/_:@=.+?,##%&~-]*[^.|\'|\\||\# |!|\(|?|\[|,| |>|<|;|\)])";
Regex r = new Regex(regex, RegexOptions.IgnoreCase);
return r.Replace(msg, "<a href=\"$1\" title=\"Click to open in a new window or tab\" target=\"_blank\">$1</a>").Replace("href=\"www", "href=\"http://www").Replace(@"\r\n", "<br />").Replace(@"\n", "<br />").Replace(@"\r", "<br />");
}
It does a good job but now I want it to exclude urls that already have a "a href=" in front. 它做得很好,但现在我希望它排除前面已经有“ a href =“的网址。 There's the ending "/a" to consider too.
也要考虑结尾“ / a”。
Can that be done with regex or have to use totally different approach, like coding? 可以使用正则表达式来完成,还是必须使用完全不同的方法(例如编码)?
Try this: 尝试这个:
((?<!href=')(?<!href=")(www\.|(http|https|ftp|news|file)+\:\/\/)[_.a-z0-9-]+\.[a-z0-9\/_:@=.+?,##%&~-]*[^.|\'|\\||\# |!|\(|?|\[|,| |>|<|;|\)])
I tested on regex101.com 我在regex101.com上测试过
With the following sample set: 使用以下示例集:
www.google.com
http://hi.com
http://www.fishy.com
href='www.ignore.com'
www.ouch.com
Using your existing regex pattern you could make a few simple changes to handle additional text being prepended or appended to your string: 使用现有的regex模式,您可以进行一些简单的更改,以处理在字符串之前或之后附加的文本:
`.+` <- pattern -> `(.+)?`
Which would give you: 这会给你:
.+((www\.|(http|https|ftp|news|file)+\:\/\/)[_.a-z0-9-]+\.[a-z0-9\/_:@=.+?,##%&~-]*[^.|\'|\\||\# |!|\(|?|\[|,| |>|<|;|\)])(.+)?
So passing the string of either: 因此,传递以下任一字符串:
<a href='http://www.test.com'>http://www.test.com</a>
...or... ...要么...
http://www.test.com
Would result in: 将导致:
<a href="http://www.test.com" title="Click to open in a new window or tab" target="_blank">www.test.com</a>
Examples: 例子:
https://regex101.com/r/bO0cW6/1 https://regex101.com/r/bO0cW6/1
I think it would be a little ToNy tHe pOny to do that in regex after all, so wrote the code, in case anyone is interested here it is: 我认为毕竟在正则表达式中这样做会有点麻烦,所以写了代码,以防万一有人对此感兴趣:
private string handleatag(string msg, string tagbegin, string tagend)
{
ArrayList tags = new ArrayList();
int tagbeginpos = msg.IndexOf(tagbegin);
int tagendpos;
string hash = tagbegin.GetHashCode().ToString();
while (tagbeginpos != -1)
{
tagendpos = msg.IndexOf(tagend, tagbeginpos);
if (tagendpos != -1)
{
string atag = msg.Substring(tagbeginpos, tagendpos - tagbeginpos + tagend.Length);
msg = msg.Replace(atag, hash + tags.Count.ToString());
tags.Add(atag);
}
else
msg = msg.Remove(tagbeginpos, tagbegin.Length);
tagbeginpos = msg.IndexOf(tagbegin, tagbeginpos);
}
msg = ConvertUrlsToLinks(msg);
for (int i = 0; i < tags.Count; i++)
msg = msg.Replace(hash + i.ToString(), tags[i].ToString());
return msg;
}
private string ConvertUrlsToLinks(string msg)
{
if (msg.IndexOf("<a href=") != -1)
return handleatag(msg, "<a href=", "</a>");
string regex = @"((www\.|(http|https|ftp|news|file)+\:\/\/)[_.a-z0-9-]+\.[a-z0-9\/_:@=.+?,##%&~-]*[^.|\'|\\||\# |!|\(|?|\[|,| |>|<|;|\)])";
Regex r = new Regex(regex, RegexOptions.IgnoreCase);
return r.Replace(msg, "<a href=\"$1\" title=\"Click to open in a new window or tab\" target=\"_blank\">$1</a>").Replace("href=\"www", "href=\"http://www").Replace(@"\r\n", "<br />").Replace(@"\n", "<br />").Replace(@"\r", "<br />");
}
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