How can I get web content with HtmlAgilityPack after login?

I'm try to develop a UWP app that get data from my University website

I'm able to login with WebView and now I'm try to extract any text that show up after login

But I try to extract web content with HtmlAgilityPack but it got redirect to login page instead.

Here is what I did

private async void GetInfo(WebView sender, WebViewDOMContentLoadedEventArgs args)
{
     HtmlDocument doc = new HtmlDocument();
     HtmlWeb web = new HtmlWeb();
     doc = await web.LoadFromWebAsync(sender.Source.AbsoluteUri);
     var chunks = new List<string>();
     foreach (var item in doc.DocumentNode.DescendantsAndSelf())
     {
         if (item.NodeType == HtmlNodeType.Text)
         {
             if (item.InnerText.Trim() != "")
             {
                 chunks.Add(item.InnerText.Trim());
             }
         }
     }
}

As I check with Visual studio, all texts in chunks list is from login page not after login page