NullReferenceException during navigation from MainPage.xaml.cs to another xaml - windows-phone-8

Question

My application takes username and password and on clinking the hyperlinkbutton, these values are sent to the server and hence server returns something like PASS:ClientID. I wish to navigate to SecondPage.xaml (from MainPage.xaml.cs) only if the responseString contains PASS.
Here is my code:
namespace aquila1
{
public partial class MainPage : PhoneApplicationPage
{
static string username;
static string password;
static string rs;
static NavigationService ns = new NavigationService();
// Constructor
public MainPage()
{
InitializeComponent();
}
private static ManualResetEvent allDone = new ManualResetEvent(true);
private void HyperlinkButton_Click_1(object sender, RoutedEventArgs e)
{
username = textbox1.Text;
password = textbox2.Text;
System.Diagnostics.Debug.WriteLine(username);
System.Diagnostics.Debug.WriteLine(password);
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://60.243.245.181/fms_tracking/php/mobile_login.php?username=" + username + "&password=" + password);
request.ContentType = "application/x-www-form-urlencoded";
// Set the Method property to 'POST' to post data to the URI.
request.Method = "POST";
// start the asynchronous operation
request.BeginGetRequestStream(new AsyncCallback(GetRequestStreamCallback), request);
// Keep the main thread from continuing while the asynchronous
// operation completes. A real world application
// could do something useful such as updating its user interface.
allDone.WaitOne();
}
private static void GetRequestStreamCallback(IAsyncResult asynchronousResult)
{
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
// End the operation
Stream postStream = request.EndGetRequestStream(asynchronousResult);
// Console.WriteLine("Please enter the input data to be posted:");
string postData = username + "+" + password;
System.Diagnostics.Debug.WriteLine(postData);
// Convert the string into a byte array.
byte[] byteArray = Encoding.UTF8.GetBytes(postData);
// Write to the request stream.
postStream.Write(byteArray, 0, postData.Length);
postStream.Close();
// Start the asynchronous operation to get the response
request.BeginGetResponse(new AsyncCallback(GetResponseCallback), request);
}
private static void GetResponseCallback(IAsyncResult asynchronousResult)
{
HttpWebRequest request = (HttpWebRequest)asynchronousResult.AsyncState;
// End the operation
HttpWebResponse response = (HttpWebResponse)request.EndGetResponse(asynchronousResult);
Stream streamResponse = response.GetResponseStream();
StreamReader streamRead = new StreamReader(streamResponse);
string responseString = streamRead.ReadToEnd();
rs = responseString;
System.Diagnostics.Debug.WriteLine(responseString);
System.Diagnostics.Debug.WriteLine("#####");
System.Diagnostics.Debug.WriteLine(rs);
// Close the stream object
streamResponse.Close();
streamRead.Close();
// Release the HttpWebResponse
response.Close();
move2();
allDone.Set();
}
private static void move2()
{
string[] rs1 = rs.Split(':');
if ((rs1[0].Trim()).Equals("PASS"))
{
ns.Navigate(new Uri("/SecondPage.xaml", UriKind.Relative));
}
else
{
MessageBox.Show(rs);
}
}
}
}
On running the code, i always get NullReferenceException .
Plz help me find the error and suggest corrections.
Thanks in advance

Answer 1

You're most likely getting the error because the NavigationService cannot find the resource /SecondPage.xaml. Is SecondPage located at the root of your project?
This can also be caused by trying to navigate before the target resource is loaded (for example, by navigating inside a page's constructor), but that doesn't immediately appear to be your problem.
This answer suggests that this problem can occur after changing namespaces or assembly names. It states that cleaning the project, ensuring all bin and obj folders are empty, then recompiling will fix it. However, its reference link is dead.