无法使用 mvvm 架构将数据绑定到 Windows Phone 中的列表框

Question

我正在尝试通过实现 mvvm 模式将来自异步回调响应的 json 对象的数据集合绑定到 windows phone 中的列表框...我能够将数据集合获取到 observablecollectionm 对象但无法绑定它到 .xaml 页面中的 UI 列表框控件。

以下是app.xaml中的代码

 public static countryListViewModel countrylistVM { get; set; }

以下是 countries.xaml 页面中的代码。

public Countries()
{
    InitializeComponent();

    if (App.countrylistVM == null)
        App.countrylistVM = new countryListViewModel();

    DataContext = App.countrylistVM;
}

protected override void OnNavigatedTo(System.Windows.Navigation.NavigationEventArgs e)
{
    base.OnNavigatedTo(e);

    if (!App.countrylistVM.IsDataLoaded)
    {
        App.countrylistVM.Loadcountries();
        App.countrylistVM.IsDataLoaded = true;
    }
}

以下是模型代码。

public class Model: INotifyPropertyChanged
{
    private Countriesdata countries;

    public Countriesdata Countries
    {
        get { return countries; }
        set
        {
            if (countries != value)
            {
                countries = value;
                RaisePropertyChanged("Countries");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged(string propname)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propname));
    }
}

}

public class Countriesdata : INotifyPropertyChanged
{
    private string countryid;

    public string Countryid
    {
        get { return countryid; }
        set
        {
            if (countryid != value)
            {
                countryid = value;
                RaisePropertyChanged("Countryid");
            }
        }
    }

    private string countryname;

    public string Countryname
    {
        get { return countryname; }
        set
        {
           if (countryname != value)
           {
               countryname = value;
               RaisePropertyChanged("Countryname");
           }
        }
    }

下面是viewmodel的代码

public class countryListViewModel : INotifyPropertyChanged
{
    HttpWebRequest crequest;
    HttpWebResponse cresponse;

    private bool isDataLoaded = false;

    public bool IsDataLoaded
    {
        get { return isDataLoaded; }

        set
        {
            if (isDataLoaded != value)
            {
                isDataLoaded = value;
                RaisePropertyChanged("IsDataLoaded");
            }
        }
    }

    private Countriesdata countries;

    public Countriesdata Countries
    {
        get { return countries; }
        set
        {
            if (countries != value)
            {
                countries = value;
                RaisePropertyChanged("Countries");
            }
        }
    }

    private ObservableCollection<Countriesdata> countrylist;

    public ObservableCollection<Countriesdata> Countrylist
    {
        get { return countrylist; }
        set
        {
            if (countrylist != value)
            {
                countrylist = value;
                RaisePropertyChanged("Countrylist");
            }
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    public void RaisePropertyChanged(string propname)
    {
        if (PropertyChanged != null)
            PropertyChanged(this, new PropertyChangedEventArgs(propname));
    }

    public void Loadcountries()
    {
        try
        {
            crequest = (HttpWebRequest)WebRequest.Create(serviceurls.getcountries);
            crequest.Accept = "application/json";
            IAsyncResult cresult = (IAsyncResult)crequest.BeginGetResponse(new AsyncCallback(Responsecallbackcountries), crequest);
        }
        catch (Exception e)
        {
        }
    }

    private void Responsecallbackcountries(IAsyncResult cresult)
    {
        try
        {
            string countryresult = string.Empty;
            cresponse = (HttpWebResponse)crequest.EndGetResponse(cresult);
            using (var Stream = cresponse.GetResponseStream())
            {
                using (var Reader = new StreamReader(Stream))
                {
                    countryresult = Reader.ReadToEnd();
                }
                JObject Country = JObject.Parse(countryresult);
                JArray Root = (JArray)Country["Countries"];

                if (Root.Count != 0)
                {
                    countrylist = new ObservableCollection<Countriesdata>();
                    var Dictionary = Root.ToDictionary(x => x, x => x);
                    JToken Tctry;

                    foreach (var cntry in Dictionary)
                    {
                        Tctry = cntry.Value;
                        countrylist.Add(
                            new Countriesdata
                            {
                                Countryid = Convert.ToString(Tctry["ID"]),
                                Countryname = Convert.ToString(Tctry["Name"])

                            });
                    }
                    System.Windows.Deployment.Current.Dispatcher.BeginInvoke(() =>
                    {
                        Views.Countries vc = new Views.Countries();
                    });
                }
            }
        }
        catch (Exception e)
        {
        }
    }
}

以下是 .xaml 页面的代码。

  <ListBox x:Name="lstcountries" 
                 Margin="0,0,-12,0"
                 ItemsSource="{Binding Countrylist}"
                 SelectedItem="{Binding Selectedcity, Mode=TwoWay}"
                 SelectionChanged="lstcountries_SelectionChanged" Background="white">
            <ListBox.ItemTemplate>
                <DataTemplate>
                    <StackPanel Orientation="Vertical" Background="Black">
                        <TextBlock Text="{Binding Countriesdata.Countryid}" Foreground="Black" 
                            Visibility="Collapsed"/>
                        <TextBlock Text="{Binding Countriesdata.Countryname}" Foreground="Black"
                           />
                    </StackPanel>
                </DataTemplate>
            </ListBox.ItemTemplate>
        </ListBox>

Answer 1

您的数据模板引用的是模型，而不是列表框绑定到的集合中的项目。

请尝试：

<DataTemplate>
    <StackPanel Orientation="Vertical">
        <TextBlock Text="{Binding Countryid}" Visibility="Collapsed"/>
        <TextBlock Text="{Binding Countryname}" />
    </StackPanel>
</DataTemplate>