在我的windows phone8应用程序中，我在列表框中显示结果。每次我在列表中只显示20个项目。
现在要显示接下来的20个项目，我想添加NEXT按钮，并显示旧项目，我想添加PREVIOUS按钮。
下面是我的代码块。在这个例子中，我使用了另一个列表框中的列表框来显示列表后面的按钮。但名单并没有滚动。

<Grid x:Name="ContentPanel" Grid.Row="3" Background="White" Margin="0,-3,0,0">
        <ListBox x:Name="outerList">
            <ScrollViewer Margin="0,0,0,0">
                <ListBox x:Name="companiesList"  SelectionChanged="companiesList_SelectionChanged" ScrollViewer.VerticalScrollBarVisibility="Auto">
                    <ListBox.ItemTemplate>
                        <DataTemplate>
                            <Grid x:Name="listItem">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="50"/>
                                    <RowDefinition Height="30"/>
                                    <RowDefinition Height="30"/>
                                    <RowDefinition Height="10"/>
                                </Grid.RowDefinitions>

                                <StackPanel x:Name="namePanel" Grid.Row="0" Orientation="Horizontal" Margin="5,0,0,5" Height="50">
                                    <TextBlock x:Name="nameTextBlock" Text="{Binding CompanyName}" Foreground="#FF501F6E" Style="{StaticResource PhoneTextNormalStyle}" HorizontalAlignment="Left" FontSize="28" MaxHeight="40" TextTrimming="WordEllipsis" Margin="0,0,0,0" Width="460" FontWeight="Bold"/>
                                </StackPanel>

                                <StackPanel x:Name="addressPanel" Grid.Row="1" Orientation="Horizontal" Margin="5,0,0,5" Height="30">
                                    <TextBlock x:Name="addressTextBlock"  Text="{Binding Address}" Foreground="#FF1F1F1F" Style="{StaticResource PhoneTextNormalStyle}" HorizontalAlignment="Left" FontSize="20" MaxHeight="30" TextTrimming="WordEllipsis" Margin="0,0,0,0" Width="460"/>
                                </StackPanel>

                                <StackPanel x:Name="phonePanel" Grid.Row="2" Orientation="Horizontal" Margin="5,0,0,0" Height="30">
                                    <Image x:Name="phone" Stretch="Uniform" Margin="0,0,0,0" Height="25" Source="Images/list_phone.png"  />
                                    <TextBlock x:Name="phoneTextBlock" Text="{Binding Phone1}" Foreground="#FF501F6E" Style="{StaticResource PhoneTextNormalStyle}" HorizontalAlignment="Left" FontSize="20" MaxHeight="30" TextTrimming="WordEllipsis" Width="460"/>
                                </StackPanel>

                                <Image  x:Name="line" Grid.Row="3" Width="460" HorizontalAlignment="Center" Source="Images/separator.png"  />
                            </Grid>
                        </DataTemplate>
                    </ListBox.ItemTemplate>
                </ListBox>
            </ScrollViewer>
            <StackPanel Height="50" Orientation="Horizontal">
                <Button Content="Previous" Height="70" HorizontalAlignment="Left" Margin="-5,1,0,0" Name="prevbutton" VerticalAlignment="Center" Width="160" Foreground="#FF501F6E">
                    <Button.Background>
                        <ImageBrush Stretch="Fill" ImageSource="Images/blank_button_nav.png"/>
                    </Button.Background>
                </Button>
                <Button Content="Next" Height="70" HorizontalAlignment="Left" Margin="170,1,0,0" Name="nextbutton" VerticalAlignment="Center" Width="160" Foreground="#FF501F6E">
                    <Button.Background>
                        <ImageBrush Stretch="Fill" ImageSource="Images/blank_button_nav.png"/>
                    </Button.Background>
                </Button>
            </StackPanel>
        </ListBox>
    </Grid>

请问你能帮我如何添加按钮的列表框是可滚动的。