用正则表达式提取图片地址问题

Question

       string str = @"(? <= <img[^>]+src="")[^""]+"; 
        Regex r = new Regex(str, RegexOptions.IgnoreCase); 
        Match m = r.Match("html代码"); 
        while (m.Success) 
        { 
            s.Add(m.Value.ToString()); 
            m = m.NextMatch(); 
        } 为什么提示正在分析“(? <= <img[^>]+src=")[^"]+)”－ 无法识别的分组构造。参数名: (? <= <img[^>]+src=")[^"]+) 如何解决。难道是正则式有问题。？？

Answer 1

string str = @"(?<=<img[^>]+src="")[^""]+";

Answer 2

string str = @"(?<= <img[^>]+src="")[^""]+"; 
        Regex r = new Regex(str, RegexOptions.IgnoreCase); 
        Match m = r.Match("html代码"); 
        while (m.Success) 
        { 
            s.Add(m.Value.ToString()); 
            m = m.NextMatch(); 
        } 

Answer 3

<(?!img)[\s\S]*?><(\/\s*)?!?((\w+:)?\w+)(\w+(\s*=?\s*(([""'])(\\[""'tbnr]|[^\7])*?\7|\w+)|.{0})|\s)*?(\/\s*)?>

Answer 4

string HTML = sr.ReadToEnd();
                    sr.Close();
                    stream.Close();
                    string pattern = @"http:\/\/[^\'\""]*\.jpg";
                    Regex reg=new Regex (pattern);
                    bool result = true;
                    if (reg.IsMatch(HTML))
                    {
                        foreach (System.Text.RegularExpressions.Match m in reg.Matches(HTML))
                        {                            
                            if (result)
                            {
                                string returnValue = DownloadImage(m.Value.ToString(),resourceId);
                                if (returnValue == "false")
                                { }
                                else
                                {
                                    result = false;
                                }
                            }
                        }
                    }
................

Answer 5

<img[\s\S\.]*?src=[\"|'](?<groupName>\.*?["|'])匹配里找组“groupName” 内容就可以了

Answer 6

            string str = "<img src=\"../Images/headerApplicationLogo.png\" />";
            string parent = "<img[\\s\\S]*?src=[\"|'](?<groupName>.*?[\"|'])";
            System.Text.RegularExpressions.Regex r = new System.Text.RegularExpressions.Regex(parent);
            
            foreach(System.Text.RegularExpressions.Match match  in  r.Matches(str))
            {
              string matchvalue =  match.Groups["groupName"].Value;
            }