Mainpage.xaml

<phone:PhoneApplicationPage
    x:Class="RedemptionHymnal.Activation"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:phone="clr-namespace:Microsoft.Phone.Controls;assembly=Microsoft.Phone"
    xmlns:shell="clr-namespace:Microsoft.Phone.Shell;assembly=Microsoft.Phone"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    FontFamily="{StaticResource PhoneFontFamilyNormal}"
    FontSize="{StaticResource PhoneFontSizeNormal}"
    Foreground="{StaticResource PhoneForegroundBrush}"
    SupportedOrientations="Portrait" Orientation="Portrait"
    mc:Ignorable="d"
    shell:SystemTray.IsVisible="True">

    <!--LayoutRoot is the root grid where all page content is placed-->
    <Grid x:Name="LayoutRoot" >
        <Grid.Background>
            <ImageBrush Stretch="Fill" ImageSource="/Assets/bg.jpg"/>
        </Grid.Background>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>

        <!--TitlePanel contains the name of the application and page title-->
        <StackPanel Grid.Row="0" Margin="12,17,0,28">
            <TextBlock Text="Redemption Hymnal" Style="{StaticResource PhoneTextNormalStyle}" Margin="12,0" FontSize="30" Foreground="Black"/>
            <TextBlock Text="Activation" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}" FontSize="50" Foreground="Black"/>
        </StackPanel>
        <PasswordBox x:Name="pin" HorizontalAlignment="Left" Margin="12,268,0,0" VerticalAlignment="Top" Width="458" SelectionForeground="#FF0A3057" BorderBrush="#FF0A3057"/>
        <TextBlock HorizontalAlignment="Left" Margin="23,236,0,0" TextWrapping="Wrap" Text="Enter Pin*" VerticalAlignment="Top" Foreground="#FF0A3057" Width="117" FontSize="24"/>
        <Button x:Name="activate" Content="Activate" HorizontalAlignment="Left" Margin="321,365,0,0" VerticalAlignment="Top" Background="#FF0A3057" BorderThickness="0" Height="70" Width="136" Click="activate_Click"/>
        <ProgressBar x:Name="pgb" HorizontalAlignment="Left" Height="18" Margin="0,184,0,0" VerticalAlignment="Top" Width="480" Background="#FF0A3057" IsIndeterminate="True" Foreground="#FF0A3057" Visibility="Collapsed"/>
        <HyperlinkButton x:Name="get" Content="Get Activation Pin" HorizontalAlignment="Left" Margin="23,365,0,0" VerticalAlignment="Top" Foreground="#FF0A3057" Click="get_Click"/>




    </Grid>

</phone:PhoneApplicationPage>
........................
mainpage.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Navigation;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Shell;
using System.Diagnostics;
using Microsoft.Phone.Tasks;

namespace RedemptionHymnal
{
    public partial class Activation : PhoneApplicationPage
    {
        public Activation()
        {
            InitializeComponent();
        }

        private void activate_Click(object sender, RoutedEventArgs e)
        {
            if (pin.Password == null || pin.Password == "")
            {
                MessageBox.Show("Please enter valid Pin");
            }
            else
            {
                Activate();
            }
        }

        public void Activate()
        {
            try
            {

           
            WebClient client = new WebClient();
            client.DownloadStringCompleted += client_DownloadStringCompleted;
            client.DownloadStringAsync(new Uri("http://iopenheavens.com/hymnalconnect/payservice.php?code=" + pin.Password.ToString() + "&device=" + App.GetID()));
            

            }
            catch (Exception ex)
            {
                MessageBox.Show("Unable to connect to Internet or server is not responding.");

                Debug.WriteLine("Error: " + ex.ToString());
            }
        }

        void client_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e)
        {
            try
            {
                if(e.Result.ToString() == "failed")
                {
                    MessageBox.Show("Wrong Activation Pin Inserted");
                }
                else
                {
                    App.SaveSetting("activation", "true");
                    MessageBox.Show("Activation Successful");
                    NavigationService.Navigate(new Uri("/MainPage.xaml", UriKind.Relative));
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Unable to connect to Internet or server is not responding.");
                Debug.WriteLine("Error: " + ex.ToString());
                
            }
            //throw new NotImplementedException();
        }

        protected override void OnNavigatedTo(NavigationEventArgs e)
        {
            if (NavigationService.BackStack.Count() == 1)
            {
                NavigationService.RemoveBackEntry();
            }
            
            base.OnNavigatedTo(e);
        }

        private void get_Click(object sender, RoutedEventArgs e)
        {
            WebBrowserTask web = new WebBrowserTask();
            web.Uri = new Uri("http://redemptionhymnal.com/buypin.html", UriKind.RelativeOrAbsolute);
            web.Show();
        }
        

        
    }
}