c# – 用于转换超链接的RegExp帮助

即

http://twitpic.com/abcdef http://www.smh.com.au askjhsd www.hotmail.com ks sd 
<a href="http://www.aaaaaaaa.com">aaaaaaaa</a>

我想要http://twitpic.com/abcdef,http：//www.smh.com.au和www.hotmail.com,但不是http://www.aaaaaaaa.com,因为它被包装围绕< a>标签已经.

我目前在C#中使用此正则表达式

return Regex.Replace(input,@"(b((http|https)://|www.)[^ ]+b)",@" <a href=""$0"" target=""_blank"">$0</a>",RegexOptions.IgnoreCase);

我不知道如何排除已包含在< a>中的内容或者< img>

救命 ：)

编辑

对于那些稍后阅读的人来说,这是我提出的最终解决方案

/// <summary>
/// Adds to the input string a target=_blank in the hyperlinks
/// </summary>
public static string ConvertURLsToHyperlinks(string input)
{
    if (!string.IsNullOrEmpty(input))
    {
        var reg = new Regex(@"(?<!<s*(?:a|img)b[^<]*)(b((http|https)://|www.)[^ ]+b)");
        return reg.Replace(input,new MatchEvaluator(ConvertUrlsMatchDelegate));

    }
    return input;
}

public static string ConvertUrlsMatchDelegate(Match m)
{
    // add in additional http:// in front of the www. for the hyperlinks
    var additional = "";
    if (m.Value.StartsWith("www."))
    {
        additional = "http://";
    }
    return "<a href="" + additional + m.Value + "" target="_blank">" + m.Value + "</a>";
}