windows store webview exception 'navCancelInit is undefined'

string username = "xxxxxx";
string password = "yyyyyy";
var handler = new HttpClientHandler();
handler.Credentials = new NetworkCredential(username, password);

HttpClient httpClient = new HttpClient(handler);

//HttpClient httpClient = new HttpClient();



HttpResponseMessage response = await httpClient.GetAsync("http://localhost:9090/");


System.Diagnostics.Debug.WriteLine("response: " + response);
string responseAsString = await response.Content.ReadAsStringAsync();
System.Diagnostics.Debug.WriteLine("response string:" + responseAsString);


webView.NavigateToString(responseAsString);



this is the code which runs and displays login.aspx in webview.... after login it redirects to userspage.aspx. but as soon as i click on login button in login.aspx after providing correct username and password, it throws that exception "navCancelInit" is undefined