WP7 将数据添加到无限列表框

Question

我正在尝试实现一个"无限"列表框，每次到达列表框末尾时都会加载新数据。当我尝试反序列化下一组搜索结果时出现问题。我正在Operation not supported on read-only collection.

这是我的课程。

public class Search
{
    //public Spellcheck spellcheck { get; set; }
    public ObservableCollection<ResultSearch> results = new ObservableCollection<ResultSearch>();
    public IEnumerator<ResultSearch> GetEnumerator()
    {
        return this.results.GetEnumerator();
    }
}
public class ResultSearch
{
    public int id { get; set; }
    public bool selected { get; set; }
    public string type { get; set; }
    public string name { get; set; }
    public bool active { get; set; }
    public string mixName { get; set; }
    public string title { get; set; }
    public string slug { get; set; }
    public object isrc { get; set; }
    public string releaseDate { get; set; }
    public string publishDate { get; set; }
    public string sampleUrl { get; set; }
    public string rtmpStreamUrl { get; set; }
    public bool exclusive { get; set; }
    public Price price { get; set; }
    //public AudioFormatFee audioFormatFee { get; set; }
    public string currentStatus { get; set; }
    public string length { get; set; }
    public int bpm { get; set; }
    public Key key { get; set; }
    public string saleType { get; set; }
    public List<SearchArtist> artists { get; set; }
    public List<SearchGenre> genres { get; set; }
    public List<object> subGenres { get; set; }
    public List<SearchChart> charts { get; set; }
    public SearchRelease release { get; set; }
    public SearchLabel label { get; set; }
    public SearchImages images { get; set; }
    //public DynamicImages dynamicImages { get; set; }
    public string bio { get; set; }
    public string url { get; set; }
}
public class SearchArtist
{
    public int id { get; set; }
    public string name { get; set; }
    public string slug { get; set; }
    public string type { get; set; }
}
public class SearchGenre
{
    public int id { get; set; }
    public string name { get; set; }
    public string slug { get; set; }
    public string type { get; set; }
}
public class SearchChart
{
    public int id { get; set; }
    public int position { get; set; }
    public string type { get; set; }
}
public class SearchRelease
{
    public int id { get; set; }
    public string name { get; set; }
    public string type { get; set; }
    public string slug { get; set; }
}
public class SearchLabel
{
    public int id { get; set; }
    public string name { get; set; }
    public string type { get; set; }
    public string slug { get; set; }
}
public class SearchImages
{
    //public Small small { get; set; }
    //public SearchMedium medium { get; set; }
    public SearchLarge large { get; set; }
    //public SearchBanner banner { get; set; }
    //public Waveform waveform { get; set; }
}
public class SearchLarge
{
    public int width { get; set; }
    public int height { get; set; }
    public string url { get; set; }
    public string secureUrl { get; set; }
}

反序列化新数据

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
    {
        base.OnNavigatedTo(e);
        string searchTxt = String.Empty;
        if (NavigationContext.QueryString.TryGetValue("searchTxt", out searchTxt))
        {
            searchTxtBox.Text = searchTxt;
            HttpUtility.UrlEncode(searchTxt);
            LaunchWebClient(searchTxt);
        }
    }
    private void LaunchWebClient(string searchTxt)
    {
        // WebClient jsonSearch
        WebClient jsonSearch = new GzipWebClient();
        Uri apiSearch = new Uri("http://api.beatport.com/catalog/3/search?query=" + searchTxt);
        jsonSearch.DownloadStringCompleted += new DownloadStringCompletedEventHandler(jsonSearch_GetDataCompleted);
        jsonSearch.DownloadStringAsync(apiSearch);
    }
    // When end of listbox is reached
    private void LaunchWebClientNextpage(int page)
    {
        int pageLimit = page;
        if (pageLimit <= 5)
        {
            // WebClient jsonSearch
            WebClient jsonSearch = new GzipWebClient();
            Uri apiSearch = new Uri("http://api.beatport.com/catalog/3/search?query=" + searchTxtBox.Text + "&page=" + page);
            jsonSearch.DownloadStringCompleted += new DownloadStringCompletedEventHandler(jsonSearchNextPage_GetDataCompleted);
            jsonSearch.DownloadStringAsync(apiSearch);
        }
        else
        {
            SystemTray.SetIsVisible(this, false);
            //SystemTray.SetOpacity(this, 0.0);
            prog.IsVisible = false;
            prog.IsIndeterminate = false;
        }
    }
    // Deserialize search json data
    public void jsonSearch_GetDataCompleted(object sender, DownloadStringCompletedEventArgs e)
    {
        Search searchData = JsonConvert.DeserializeObject<Search>(e.Result);
        if (searchData.results.Count == 0)
        {
            MessageBox.Show("your search didn't return any results");
        }
        else
        {
            this.listSearch.ItemsSource = searchData.results;
        }
    }
    // Deserialize search next page json data
    public void jsonSearchNextPage_GetDataCompleted(object sender, DownloadStringCompletedEventArgs e)
    {
        Search searchDataPage = JsonConvert.DeserializeObject<Search>(e.Result);
        //listSearch.Items.Add(searchDataPage.results);
    }

感谢您的帮助。

更新

这也是我的xaml

<!--ContentPanel - place additional content here-->
    <Grid x:Name="ContentPanel" Grid.Row="1" Margin="12,0,12,0">            
        <ListBox x:Name="listSearch" >
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Horizontal" >
                        <Image delay:LowProfileImageLoader.UriSource="{Binding images.medium.url}" Tap="searchSelectedImageHandler" Margin="10" Width="60" Height="60" />
                        <StackPanel Orientation="Vertical" >
                            <TextBlock Text="{Binding name}" Tap="searchSelectedHandler" Style="{StaticResource PhoneTextLargeStyle}"/>
                            <TextBlock Text="{Binding type}" Style="{StaticResource PhoneTextSubtleStyle}" />
                        </StackPanel>
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>
    </Grid>

Answer 1

发布的代码有一个带有ObservableCollection的class Search：

public ObservableCollection<ResultSearch> results = new ObservableCollection<ResultSearch>();

但是，反序列化正在尝试添加到listSearch：

listSearch.Items.Add(searchDataPage.results);

我怀疑，这些项目应该添加到results集合中，而不是listSearch控件中。

编辑以回复评论：

这里要做的最快（不是最理想）的事情是在代码隐藏中创建可观察集合，然后将列表框的 ItemsSource 设置为 ObservableCollection 并修改 json 方法：

// code behind for your xaml
public partial class MyCodeBehind
{
  public ObservableCollection<Search> Searches;
  public MyCodeBehind()
  {
    InitializeComponent();
    Searches = new ObservableCollection<Search>();
    // bind the collection to the ListBox
    this.listSearch.ItemsSource = Searches;
  }
  // Deserialize search json data
  public void jsonSearch_GetDataCompleted(object sender, DownloadStringCompletedEventArgs e)
  {
    Search searchData = JsonConvert.DeserializeObject<Search>(e.Result);
    if (searchData.results.Count == 0)
    {
      MessageBox.Show("your search didn't return any results");
    }
    else
    {
      // add the results to the existing Searches collection
      foreach (Search search in searchData.results)
      {
        Searches.Add(search);
      }
    }
  }
  // Deserialize search next page json data
  public void jsonSearchNextPage_GetDataCompleted(object sender, DownloadStringCompletedEventArgs e)
  {
    Search searchDataPage = JsonConvert.DeserializeObject<Search>(e.Result);
    // add the results to the existing Searches collection
    foreach (Search search in searchDataPage)
    {
      Searches.Add(search);
    }
  }
}