Can't access hub elements from class

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C#

Windows

XAML

Win8

I had a xaml in mainpage and want to access it's elements like x:Name="D1P1" in a c# class but can't use it and get an error the name "D1P1" does not exist in the current context any idea how to access the hub elements in c# class I use FindName but it did't work

<HubSection Width="950" x:Name="DayOneTimeHubSection" Margin="20,0,0,0">
                <DataTemplate>
                    <Grid>
                        <StackPanel Orientation="Vertical">
                            <StackPanel Orientation="Horizontal" Height="180" Margin="0,0,0,-15">
                                <StackPanel Width="280" Height="160" Background="#FF253842" Margin="05,0,0,0">
                                    <TextBlock x:Name="D1P1"  HorizontalAlignment="Center" LineHeight="80" TextWrapping="Wrap"  FontSize="64" TextAlignment="Center" Foreground="#FFB0B1B2" FontFamily="Arial Narrow" Margin="0,10,0,0" />
                                    <TextBlock x:Name="D1NP1" HorizontalAlignment="Center" VerticalAlignment="Bottom" LineHeight="64" TextWrapping="Wrap"  FontSize="64" TextAlignment="Center" Foreground="White" FontFamily="DengXian" Margin="30,0" />
                                </StackPanel>

                       </StackPanel>

                </StackPanel>

</Grid>

</DataTemplate>

</hubsection>