c# - Need to replace href of anchor tags in a string

Question

string content=" 
        <br /><br /><a href="need to replace this url">Cooking School</a><br /><br /><a href="http://www.sdlm.com">Feed your senses</a><br /><br /><a href="http://www.sdl.com">Take your cooking skills to the next level. Find a cooking school near you!</a><br /><br /><a href="http:google.com"><img src="http://www.sdlm1.com/autd3umrl_u_t.jpg" /></a>
     "

I need to replace all anchor tags href value with different urls I used the following function but its getting error

 public List<string> GetLinksFromHtml(string content)
        {
            string regex = @"<(?<Tag_Name>(a)|img)[^>]*?(?<URL_Type>(?(1)href|src))s*=s*(?:""(?<URL>(?:""|[^""])*)""|'(?<URL>(?:\'|[^'])*)'))";
            var matches = Regex.Matches(content, regex, RegexOptions.IgnoreCase | RegexOptions.Singleline);
            var links = new List<string>();

            foreach (Match item in matches)
            {
                string link = item.Groups[1].Value;
                links.Add(link);
            }

            return links;
        }

Thanks for any help

Answer 1

Trying to parse html with regex is not a good idea. See this post. Use a real html parser like HtmlAgilityPack .

HtmlAgilityPack.HtmlDocument doc = new HtmlAgilityPack.HtmlDocument();
doc.LoadHtml(content);
foreach (var a in doc.DocumentNode.Descendants("a"))
{
    a.Attributes["href"].Value = "http://a.com?url=" + HttpUtility.UrlEncode(a.Attributes["href"].Value);
}

var newContent = doc.DocumentNode.OuterHtml;