Install-Package HtmlAgilityPack

// From File
var doc = new HtmlDocument();
doc.Load(filePath);

// From String
var doc = new HtmlDocument();
doc.LoadHtml(html);

// From Web
var url = "http://html-agility-pack.net/";
var web = new HtmlWeb();
var doc = web.Load(url);

// With XPath    
var value =http://www.mamicode.com/ doc.DocumentNode
    .SelectNodes("//td/input")
    .First()
    .Attributes["value"].Value;
    
// With LINQ    
var nodes = doc.DocumentNode.Descendants("input")
    .Select(y => y.Descendants()
    .Where(x => x.Attributes["class"].Value =http://www.mamicode.com/= "box"))
    .ToList();

HtmlWeb webClient = new HtmlWeb();
HtmlDocument doc = webClient.Load("http://www.cnsos.net/weburl/");

HtmlNodeCollection hrefList = doc.DocumentNode.SelectNodes(".//a[@href]");

if (hrefList != null)
{
    foreach (HtmlNode href in hrefList)
    {
        HtmlAttribute att = href.Attributes["href"];
        Console.WriteLine(att.Value);
    }
}