c# - HTML parsing with HtmlAgilityPack in Windows Store App -

i'm parsing html code image link in "windows store application" i'm using html agility pack ! here code :

    async void loidcontent()         {             foreach (var feeditem in feeddata.items)             {                httpclient httpclient  = new httpclient();                var stream = await httpclient.getstreamasync(feeditem.link);                htmldocument htmldoc = new htmldocument();                 htmldoc.load(stream);                  // image                 var div = htmldoc.documentnode.descendants().firstordefault(                     d =>                     d.name == "div" && d.attributes["class"] != null && d.attributes["class"].value == "pika-stage img");                  var img = div.descendants("img").firstordefault();                 if (img != null)                 {                     string imglinks = img.attributes["src"].value;                     feeditem.image = new uri(imglinks);                 } }} 

sometimes application crashes "object reference not set instance of object" in line

var img = div.descendants("img").firstordefault(); 

before this:

var img = div.descendants("img").firstordefault(); 

check null:

if ((div != null) && (div.descendants("img") != null)) {     // rest of code }