如何在需求中添加枢轴项中的内容

Question

我正在努力使用枢轴项目内容来按需添加内容，但所有项目都会立即添加。 （数据库标题的加载）

我在MainViewModel下面使用。

public class ArabicTextTranslationViewModel : INotifyPropertyChanged
    {
        ObservableCollection<ArabicTextTranslationHeader> _arabicTextTranslationHeader;
        public ArabicTextTranslationViewModel()
        {
            ArabicTextTranslationHeaders = new ObservableCollection<ArabicTextTranslationHeader>();
            DataSource ds = new DataSource();
            List<Chapter> chapters = ds.getChaptersIndex(); // has 114 pivot headers
            List<ArabicTextWithTranslationContent> content = null;
            foreach (Chapter chapter in chapters)
            {
                content = ds.getArabicTextTranslationContent(chapter);
                ArabicTextTranslationHeaders.Add(new ArabicTextTranslationHeader() { Header = chapter.TName, ArabicTextWithTranslationContent = content }); //loading contents
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        public void OnPropertyChanged(string propertyName)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
            }
        }

        public ObservableCollection<ArabicTextTranslationHeader> ArabicTextTranslationHeaders
        {
            get { return _arabicTextTranslationHeader; }
            set
            {
                if (_arabicTextTranslationHeader != value)
                {
                    _arabicTextTranslationHeader = value;
                    OnPropertyChanged("ArabicTextTranslationHeaders");
                }
            }
        }


        public class ArabicTextTranslationHeader : INotifyPropertyChanged
        {
            public event PropertyChangedEventHandler PropertyChanged;
            public void OnPropertyChanged(string propertyName)
            {
                if (PropertyChanged != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
                }
            }

            string _header;
            public string Header
            {
                get { return _header; }
                set
                {
                    if (_header != value)
                    {
                        _header = value;
                        OnPropertyChanged("Header");
                    }
                }
            }

            List<ArabicTextWithTranslationContent> _arabicTextTranslationContent;
            public List<ArabicTextWithTranslationContent> ArabicTextWithTranslationContent
            {
                get { return _arabicTextTranslationContent; }
                set
                {
                    if (_arabicTextTranslationContent != value)
                    {
                        _arabicTextTranslationContent = value;
                        OnPropertyChanged("ArabicTextWithTranslationContent");
                    }
                }
            }
        }
        public class ArabicTextWithTranslationContent : INotifyPropertyChanged
        {
            public event PropertyChangedEventHandler PropertyChanged;
            public void OnPropertyChanged(string propertyName)
            {
                if (PropertyChanged != null)
                {
                    PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
                }
            }

            List<ArabicTextWithTranslation> _arabicTextTranslation;
            public List<ArabicTextWithTranslation> ArabicTextWithTranslation
            {
                get { return _arabicTextTranslation; }
                set
                {
                    if (_arabicTextTranslation != value)
                    {
                        _arabicTextTranslation = value;
                        OnPropertyChanged("ArabicTextWithTranslation");
                    }
                }
            }

        }
    }

和XAML

<phone:Pivot Title="{Binding Path=LocalizedResources.ApplicationTitle, Source={StaticResource LocalizedStrings}}" 
                     ItemsSource="{Binding ArabicTextTranslationHeaders}"
                    DataContext="{Binding Source={StaticResource ArabicTextTranslationDataSource}}">
            <phone:Pivot.HeaderTemplate>
                <DataTemplate>
                    <TextBlock Text="{Binding Header}"></TextBlock>
                </DataTemplate>
            </phone:Pivot.HeaderTemplate>
            <phone:Pivot.ItemTemplate>
                <DataTemplate>
                    <ListBox ItemsSource="{Binding ArabicTextWithTranslationContent}"
                             FontFamily="./Fonts/ScheherazadeRegOT.ttf#Scheherazade" 
                             FlowDirection="RightToLeft" Foreground="Black" >
                        <ListBox.ItemTemplate>
                            <DataTemplate>
                                <ItemsControl ItemsSource="{Binding ArabicTextWithTranslation}">
                                    <ItemsControl.ItemTemplate>
                                        <DataTemplate>
                                            <StackPanel Orientation="Vertical">
                                                <TextBlock TextWrapping="Wrap" 
                                                   Text="{Binding ArabicText.Aya}" FontSize="30" 
                                                   Foreground="Black"></TextBlock>
                                            </StackPanel>
                                        </DataTemplate>
                                    </ItemsControl.ItemTemplate>
                                </ItemsControl>
                            </DataTemplate>
                        </ListBox.ItemTemplate>
                    </ListBox>
                </DataTemplate>
            </phone:Pivot.ItemTemplate>
        </phone:Pivot>

问题是，我遇到内存不足异常，我发现所有内容都是立即加载的。

如何按需加载每个透视图项目的内容？