正则表达式可能是此类任务的朋友:

Regular expressions are probably your friend for this kind of task:

Regex r = new Regex(@"(https?://[^s]+)");
myString = r.Replace(myString, "<a href="$1">$1</a>");

匹配 URL 的正则表达式可能需要一些工作.

The regular expression for matching URLs might need a bit of work.