TextBlock1 is not declared. It may be inaccessible due to its protection level

TextBlock1 is not declared. It may be inaccessible due to its protection
level

As silly as this sounds im a little stomped at this one. Heres my XAML in
a Win Phone 8 App:
<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="Transparent">
<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="MY APPLICATION" Style="{StaticResource
PhoneTextNormalStyle}"/>
<TextBlock Text="Page" Margin="9,-7,0,0" Style="{StaticResource
PhoneTextTitle1Style}"/>
</StackPanel>
<!--ContentPanel - place additional content here-->
<Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">
<phone:LongListSelector x:Name="MainLongListSelector"
Margin="0,0,-12,0" ItemsSource="{Binding Items}"
SelectionChanged="MainLongListSelector_SelectionChanged">
<phone:LongListSelector.ItemTemplate>
<DataTemplate>
<StackPanel Margin="0,0,0,17">
<TextBlock x:Name="TextBlock1"
HorizontalAlignment="Left" TextWrapping="Wrap"
VerticalAlignment="Top"/>
</StackPanel>
</DataTemplate>
</phone:LongListSelector.ItemTemplate>
</phone:LongListSelector>
</Grid>
</Grid>
Ive searched around but i dont know why i cant write code against the
TextBlock1 control in code behind. When i type TextBlock1.Text= .... i get
the error TextBlock1 is not declared. It may be inaccessible due to its
protection level. but i cant see how its private?
All im trying to do is add a textblock assign some content to it and then
that selected value is then passed across another page to perform relevant
action.
In addition as soon as i remove it outside of the PhoneListSelector i can
access it!!