HTML Agility pack - parsing img src and href from relative paths

I cant test or run this now, but you can try something like that:

var htmlStr = "yourhtml";
var doc = new HtmlDocument();
doc.LoadHtml(htmlStr);
var baseUri = new Uri("baseUriOfYourSite");
var images = doc.DocumentNode.SelectNodes("//img/@src").ToList();
var links = doc.DocumentNode.SelectNodes("//a/@href").ToList();
foreach (var item in images.Concat(links))
{
    item.InnerText =  new Uri(baseUri, item.InnerText).AbsoluteUri;    
}