title: Undeclared Prefix. How do I declare in Windows Phone?
body: <p>I am trying to follow <a href="http://gavindraper.com/2013/01/14/mvvm-page-navigation-using-mvvm-light-on-wp7/" rel="nofollow">this tutorial</a> but I keep runnning into problems on Step 4. I get this error and I don't know how to fix it.</p>
  
  <pre><code>Error   1   'mvvmnavigation' is an undeclared prefix. Line 1, position 2.
  
  
  &lt;mvvmnavigation:baseapplicationpage 
      x:Class="MVVMNavigation.MainPage"
      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"
      mc:Ignorable="d" d:DesignWidth="480" d:DesignHeight="768"
      FontFamily="{StaticResource PhoneFontFamilyNormal}"
      FontSize="{StaticResource PhoneFontSizeNormal}"
      Foreground="{StaticResource PhoneForegroundBrush}"
      SupportedOrientations="Portrait" Orientation="Portrait"
      shell:SystemTray.IsVisible="True"&gt;
  
      &lt;!--LayoutRoot is the root grid where all page content is placed--&gt;
      &lt;Grid x:Name="LayoutRoot" Background="Transparent"&gt;
          &lt;Grid.RowDefinitions&gt;
              &lt;RowDefinition Height="Auto"/&gt;
              &lt;RowDefinition Height="*"/&gt;
          &lt;/Grid.RowDefinitions&gt;
  
          &lt;!--TitlePanel contains the name of the application and page title--&gt;
          &lt;StackPanel x:Name="TitlePanel" Grid.Row="0" Margin="12,17,0,28"&gt;
              &lt;TextBlock x:Name="ApplicationTitle" Text="MY APPLICATION" Style="{StaticResource PhoneTextNormalStyle}"/&gt;
              &lt;TextBlock x:Name="PageTitle" Text="page name" Margin="9,-7,0,0" Style="{StaticResource PhoneTextTitle1Style}"/&gt;
          &lt;/StackPanel&gt;
  
          &lt;!--ContentPanel - place additional content here--&gt;
          &lt;Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0"&gt;&lt;/Grid&gt;
      &lt;/Grid&gt;
  
      &lt;!--Sample code showing usage of ApplicationBar--&gt;
      &lt;!--&lt;phone:PhoneApplicationPage.ApplicationBar&gt;
          &lt;shell:ApplicationBar IsVisible="True" IsMenuEnabled="True"&gt;
              &lt;shell:ApplicationBarIconButton IconUri="/Images/appbar_button1.png" Text="Button 1"/&gt;
              &lt;shell:ApplicationBarIconButton IconUri="/Images/appbar_button2.png" Text="Button 2"/&gt;
              &lt;shell:ApplicationBar.MenuItems&gt;
                  &lt;shell:ApplicationBarMenuItem Text="MenuItem 1"/&gt;
                  &lt;shell:ApplicationBarMenuItem Text="MenuItem 2"/&gt;
              &lt;/shell:ApplicationBar.MenuItems&gt;
          &lt;/shell:ApplicationBar&gt;
      &lt;/phone:PhoneApplicationPage.ApplicationBar&gt;--&gt;
  
  &lt;/mvvmnavigation:baseapplicationpage&gt;
  </code></pre>
  
  <p>my codebehind</p>
  
  <pre><code>namespace MVVMNavigation
  {
      public partial class MainPage : MVVMNavigation.BaseApplicationPage
      {
          // Constructor
          public MainPage()
          {
              InitializeComponent();
          }
      }
  }
  </code></pre>
  
  <p>Base App</p>
  
  <pre><code>using System;
  using GalaSoft.MvvmLight.Messaging;
  using Microsoft.Phone.Controls;
  
  namespace MVVMNavigation
  {
      public class BaseApplicationPage : PhoneApplicationPage
      {
          public void NavigateTo(Uri uri)
          {
              if (uri.ToString() == "/GoBack.xaml")
                  NavigationService.GoBack();
              else
                  NavigationService.Navigate(uri);
          }
  
          protected override void OnNavigatedFrom(System.Windows.Navigation.NavigationEventArgs e)
          {
              Messenger.Default.Unregister&lt;Uri&gt;(this);
              base.OnNavigatedFrom(e);
          }
  
          protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
          {
              Messenger.Default.Register&lt;Uri&gt;(this, "NavigationRequest", NavigateTo);
              base.OnNavigatedTo(e);
          }
      }
  }
  </code></pre>