Passing values in xaml pages

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C#

Windows

C#4.0

Been atempting to pass values in xaml page to another.Help with the code below

Page 1

private void btnEmailLogin_Click(object sender, RoutedEventArgs e)
       {
            string emailAddress = txtEmailAddress.Text;
           string txtPasswords = txtPassword.Text;
           NavigationService.Navigate(new Uri(string.Format("/EmailSender.xaml?emailAddress={0}&txtPasswords={1}", emailAddress, txtPasswords), UriKind.Relative));


       }

Page 2

if (this.NavigationContext.QueryString.ContainsKey("emailAddress") || this.NavigationContext.QueryString.ContainsKey("password"))
            {
               this.txtFrom.Text = this.NavigationContext.QueryString["emailAddress"];
                       }

I get a nullRefrenceException in the if statement...Need help