How to Get data in WebBrowser

Windows Form has WebBrowser Control, button "Login" and button "Get data" (Windows Control). When i click button Login: login website A (I passed). When i logined, WebBrowser return 3 frame (top frame, left frame and center frame).  Center frame shows all product (product name, product price, ...). After 1 minute, this frame refresh. This frame has:   
   
 The follow result in browser:   How to get this result when i click button "Get data"?

I use code:

HtmlDocument objHTMLDoc = webBrowserIbet.Document;
string strUrl = webBrowserIbet.Url.ToString();  // www.abc.com/main.aspx
strUrl = strUrl.Replace("main.aspx", "GetPrice.aspx?hidPID=123&hidC=5");
string strContent = "";
HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(strUrl);
myRequest.Method = "GET";
myRequest.ContentType = "text/html; charset=utf-8";
myRequest.Referer = webBrowserIbet.Url.ToString();
myRequest.CookieContainer = new CookieContainer();
Uri uri = new Uri(strUrl);
myRequest.CookieContainer.SetCookies(uri, webBrowserIbet.Document.Cookie);
HttpWebResponse myResponse = (HttpWebResponse)myRequest.GetResponse();
using (StreamReader sr = new StreamReader(myResponse.GetResponseStream()))
{
strContent = sr.ReadToEnd();
sr.Close();
}
myResponse.Close();

But result is empty not 


Help me!!!!!!