listbox.xaml

<ListBox Name="lstPosts" Margin="0,10,0,0" ItemsSource="{Binding SelectedSite.Posts}" Grid.Row="2" SelectedItem="{Binding SelectedPost, Mode=TwoWay}">

                    <ListBox.ItemTemplate>
                        <DataTemplate>                            

                            <Border BorderBrush="{StaticResource PhoneForegroundBrush}" CornerRadius="20" BorderThickness="0 0 0 2" Margin="0 2" >
                                <TextBlock Text="{Binding Title}" TextWrapping="Wrap" Style="{StaticResource PhoneTextLargeStyle}" Width="{Binding ElementName=lstPosts, Path=ActualWidth}"/>
                            </Border>
                            
                        </DataTemplate>
                    </ListBox.ItemTemplate>

                </ListBox>
            

        </Grid>