listbox.itemssource_binding…不起作用,但是如果我用代码设置itemssource,那就太好了!

我正在使用WPF进行试验,遇到了一个似乎无法解决的问题,尽管我以前在Silverlight上做过一些工作,并且成功地使用了DataContexts、数据绑定和INPC。这次我被卡住了…

我正在使用此代码创建应用程序主窗口的实例:

protected override void OnStartup(StartupEventArgs e)
{
    base.OnStartup(e);
    MainWindow window = new MainWindow();
    var viewModel = new MainVM(); //implements INotifyPropertyChanged
    viewModel.Load("Brighton+UK");
    window.DataContext = viewModel;
    window.weatherList.ItemsSource = viewModel.WeatherInfo; //THIS WORKS
    window.Show();
}

当我像这样运行应用程序时,一切都很好,主窗口上的列表框会像应该的那样显示在MainVM的WeatherInfo ObservableCollection中找到的项目。

但是,当我对该行进行注释,然后进入主窗口的xaml,并在xaml中设置weatherlist列表框的itemssource属性时,如下所示:

<ListBox x:Name="weatherList" 
    Grid.Row="0" 
    ItemContainerStyle="{StaticResource stretched}" 
    ItemsSource="{Binding WeatherInfo}" />

虽然我确实将mainWindow的dataContext设置为mainVM的一个实例(如C代码摘要所示),但列表并不会像我预期的那样被填充。

有人能给我解释一下,为什么?

=编辑=

所有主窗口的XAML:

<Window x:Class="DataTemplates.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="Google World Weather" 
        SizeToContent="WidthAndHeight" 
        WindowStartupLocation="CenterScreen"
        xmlns:local="clr-namespace:DataTemplates" >

    <!--Resources section-->
    <Window.Resources>

        <!--Styles-->
        <Style TargetType="Label">
            <Setter Property="FontSize" Value="24" />
            <Setter Property="Margin" Value="10,0,0,0" />
        </Style>

        <Style x:Key="stretched" TargetType="ListBoxItem">
            <Setter Property="HorizontalContentAlignment" Value="Stretch" />
        </Style>

    </Window.Resources>

    <!--Command binding definition-->
    <Window.CommandBindings>
        <CommandBinding Command="Refresh" x:Name="cmdLoadWeatherForecast" CanExecute="cmdLoadWeatherForecast_CanExecute" Executed="cmdLoadWeatherForecast_Executed" />
    </Window.CommandBindings>

    <!--UI design - layout of individual controls-->
    <Grid x:Name="LayoutRoot">
        <Grid.RowDefinitions>
            <RowDefinition Height="*" />
            <RowDefinition Height="Auto" />
        </Grid.RowDefinitions>

        <ListBox x:Name="weatherList" Grid.Row="0" ItemContainerStyle="{StaticResource stretched}" ItemsSource="{Binding WeatherInfo}" />

        <StackPanel Grid.Row="1" Orientation="Horizontal" HorizontalAlignment="Center" Margin="10" >
            <TextBox Text="Brighton UK" Name="txtLocation" Width="200" FontSize="20" Margin="10" FocusManager.FocusedElement="{Binding txtLocation}" />
            <Button IsDefault="True" Name="btnLoadForecast" Content="Load Weather Forecast"  Command="Refresh" Margin="0,10,10,10" Padding="10"/>
        </StackPanel>

    </Grid>
</Window>