我正在开发一个使用本地数据库和 MVVM 的 Windows Phone 应用程序。我的列表框没有显示它绑定到的 WeatherList。我在 App.xaml.cs 文件中将单个 WeatherItem 添加到本地数据库，并且已成功添加，但在运行应用程序时它未显示在列表框中。我真的很感激任何帮助。我有以下设置：
MainPage.xaml：
<phone:PhoneApplicationPage.Resources>
<DataTemplate x:Key="ForecastListItemTemplate">
<StackPanel Orientation="Horizontal" Margin="0, 400, 0, 0" Width="480" Height="100">
<StackPanel Width="190" VerticalAlignment="Center">
<TextBlock HorizontalAlignment="Center" Text="{Binding Path=DayOfWeek}" FontFamily="Segoe WP" FontWeight="ExtraBold" FontSize="36" Foreground="#545d61"></TextBlock>
<TextBlock HorizontalAlignment="Center" Text="{Binding Path=ItemDay}" FontFamily="Segoe WP Light" FontSize="36" Foreground="#545d61"></TextBlock>
</StackPanel>
<Image Height="100" Width="100" Source="{Binding Path=ImageSource}"></Image>
<StackPanel Width="190" VerticalAlignment="Center">
<StackPanel HorizontalAlignment="Center" Orientation="Horizontal">
<TextBlock Text="↑" FontFamily="Segoe WP" FontWeight="ExtraBold" FontSize="36" Foreground="#545d61"></TextBlock>
<TextBlock HorizontalAlignment="Center" Margin="4, 0, 4, 0" Text="{Binding Path=High}" FontFamily="Segoe WP" FontWeight="ExtraBold" FontSize="36" Foreground="#0da5d0"></TextBlock>
<TextBlock Text="↓" FontFamily="Segoe WP" FontWeight="ExtraBold" FontSize="36" Foreground="#545d61"></TextBlock>
<TextBlock HorizontalAlignment="Center" Margin="4, 0, 4, 0" Text="{Binding Path=Low}" FontFamily="Segoe WP" FontWeight="ExtraBold" FontSize="36" Foreground="#0da5d0"></TextBlock>
</StackPanel>
<TextBlock HorizontalAlignment="Center" Text="{Binding Path=Condition}" FontFamily="Segoe WP Light" FontSize="24" Foreground="#545d61"></TextBlock>
</StackPanel>
</StackPanel>
</DataTemplate>
</phone:PhoneApplicationPage.Resources>
<!--LayoutRoot is the root grid where all page content is placed-->
<Grid x:Name="LayoutRoot" Background="#e1e4e4">
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<ListBox
x:Name="WeatherListBox"
ItemsSource="{Binding WeatherList}"
Margin="0, 400, 0, 96"
Width="480"
ItemTemplate="{StaticResource ForecastListItemTemplate}">
</ListBox>
</Grid>
WeatherViewModel.cs
public class WeatherViewModel : INotifyPropertyChanged
{
// LINQ to SQL data context for the local database.
private ToDoDataContext weatherDB;
// Class constructor, create the data context object.
public WeatherViewModel()
{
weatherDB = new ToDoDataContext();
}
// All to-do items.
private ObservableCollection<WeatherItem> _weatherList;
public ObservableCollection<WeatherItem> WeatherList
{
get { return _weatherList; }
set
{
_weatherList = value;
NotifyPropertyChanged("WeatherList");
}
}
// Write changes in the data context to the database.
public void SaveChangesToDB()
{
weatherDB.SubmitChanges();
}
// Query database and load the collections and list used by the pivot pages.
public void LoadCollectionsFromDatabase()
{
// Specify the query for all to-do items in the database.
var weatherItemsInDB = from WeatherItem weather in weatherDB.Forecasts
select weather;
// Query the database and load all to-do items.
WeatherList = new ObservableCollection<WeatherItem>(weatherItemsInDB);
}
// Add a to-do item to the database and collections.
public void AddWeatherItem(WeatherItem newWeatherItem)
{
// Add a to-do item to the data context.
weatherDB.Forecasts.InsertOnSubmit(newWeatherItem);
// Save changes to the database.
weatherDB.SubmitChanges();
// Add a to-do item to the "all" observable collection.
WeatherList.Add(newWeatherItem);
}
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
// Used to notify Silverlight that a property has changed.
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
}
ToDoDataContext.cs
public class ToDoDataContext : DataContext
{
// Pass the connection string to the base class.
public ToDoDataContext()
: base("Data Source=isostore:/AppDB.sdf")
{ }
public ToDoCategory activeCategory;
// Specify a table for the to-do items.
public Table<ToDoItem> Items;
// Specify a table for the categories.
public Table<ToDoCategory> Categories;
//Weather stuff
public WeatherItem currentWeather;
// Specify a table for the to-do items.
public Table<WeatherItem> Forecasts;
}
[Table]
public class WeatherItem : INotifyPropertyChanged, INotifyPropertyChanging
{
// Define ID: private field, public property, and database column.
private int _weatherItemId;
[Column(IsPrimaryKey = true, IsDbGenerated = true, DbType = "INT NOT NULL Identity", CanBeNull = false, AutoSync = AutoSync.OnInsert)]
public int WeatherItemId
{
get { return _weatherItemId; }
set
{
if (_weatherItemId != value)
{
NotifyPropertyChanging("WeatherItemId");
_weatherItemId = value;
NotifyPropertyChanged("WeatherItemId");
}
}
}
// Define item name: private field, public property, and database column.
private string _itemDay;
[Column]
public string ItemDay
{
get { return _itemDay; }
set
{
if (_itemDay != value)
{
NotifyPropertyChanging("ItemDay");
_itemDay = value;
NotifyPropertyChanged("ItemDay");
}
}
}
private string _dayOfWeek;
[Column]
public string DayOfWeek
{
get { return _dayOfWeek; }
set
{
if (_dayOfWeek != value)
{
NotifyPropertyChanging("DayOfWeek");
_dayOfWeek = value;
NotifyPropertyChanged("DayOfWeek");
}
}
}
// Define completion value: private field, public property, and database column.
private string _high;
[Column]
public string High
{
get { return _high; }
set
{
if (_high != value)
{
NotifyPropertyChanging("High");
_high = value;
NotifyPropertyChanged("High");
}
}
}
private string _low;
[Column]
public string Low
{
get { return _low; }
set
{
if (_low != value)
{
NotifyPropertyChanging("Low");
_low = value;
NotifyPropertyChanged("Low");
}
}
}
private string _condition;
[Column]
public string Condition
{
get { return _condition; }
set
{
if (_condition != value)
{
NotifyPropertyChanging("Condition");
_condition = value;
NotifyPropertyChanged("Condition");
}
}
}
private string _imageSource;
[Column]
public string ImageSource
{
get { return _imageSource; }
set
{
if (_imageSource != value)
{
NotifyPropertyChanging("ImageSource");
_imageSource = value;
NotifyPropertyChanged("ImageSource");
}
}
}
// Version column aids update performance.
[Column(IsVersion = true)]
private Binary _version;
#region INotifyPropertyChanged Members
public event PropertyChangedEventHandler PropertyChanged;
// Used to notify that a property changed
private void NotifyPropertyChanged(string propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
#endregion
#region INotifyPropertyChanging Members
public event PropertyChangingEventHandler PropertyChanging;
// Used to notify that a property is about to change
private void NotifyPropertyChanging(string propertyName)
{
if (PropertyChanging != null)
{
PropertyChanging(this, new PropertyChangingEventArgs(propertyName));
}
}
#endregion
}
主页.xaml.cs
// Constructor
public MainPage()
{
InitializeComponent();
this.DataContext = App.WeatherViewModel;
}
应用程序.xaml.cs
public partial class App : Application
{
private static ToDoViewModel viewModel;
public static ToDoViewModel ViewModel
{
get { return viewModel; }
}
private static WeatherViewModel weatherViewModel;
public static WeatherViewModel WeatherViewModel
{
get { return weatherViewModel; }
}
/// <summary>
/// Provides easy access to the root frame of the Phone Application.
/// </summary>
/// <returns>The root frame of the Phone Application.</returns>
public PhoneApplicationFrame RootFrame { get; private set; }
/// <summary>
/// Constructor for the Application object.
/// </summary>
public App()
{
// Global handler for uncaught exceptions.
UnhandledException += Application_UnhandledException;
// Standard Silverlight initialization
InitializeComponent();
// Phone-specific initialization
InitializePhoneApplication();
// Show graphics profiling information while debugging.
if (System.Diagnostics.Debugger.IsAttached)
{
// Display the current frame rate counters.
Application.Current.Host.Settings.EnableFrameRateCounter = true;
// Show the areas of the app that are being redrawn in each frame.
//Application.Current.Host.Settings.EnableRedrawRegions = true;
// Enable non-production analysis visualization mode,
// which shows areas of a page that are handed off to GPU with a colored overlay.
//Application.Current.Host.Settings.EnableCacheVisualization = true;
// Disable the application idle detection by setting the UserIdleDetectionMode property of the
// application's PhoneApplicationService object to Disabled.
// Caution:- Use this under debug mode only. Application that disables user idle detection will continue to run
// and consume battery power when the user is not using the phone.
PhoneApplicationService.Current.UserIdleDetectionMode = IdleDetectionMode.Disabled;
}
// Create the database if it does not exist.
using (ToDoDataContext db = new ToDoDataContext())
{
if (db.DatabaseExists() == false)
{
// Create the local database.
db.CreateDatabase();
// Prepopulate the categories.
db.Categories.InsertOnSubmit(new ToDoCategory { Name = "Home" });
db.Categories.InsertOnSubmit(new ToDoCategory { Name = "Work" });
db.Categories.InsertOnSubmit(new ToDoCategory { Name = "School" });
db.Forecasts.InsertOnSubmit(new WeatherItem
{
DayOfWeek = "Mon",
ItemDay = "Sept 4",
Condition = "Mostly Sunny",
High = "105",
Low = "88",
ImageSource = "images/Weather/45.png"
});
// Save categories to the database.
db.SubmitChanges();
}
}
// Create the ViewModel object.
viewModel = new ToDoViewModel();
weatherViewModel = new WeatherViewModel();
// Query the local database and load observable collections.
viewModel.LoadCollectionsFromDatabase();
weatherViewModel.LoadCollectionsFromDatabase();
}
谢谢！