Question

我有一个简单的UserControl，DropDown显示版本，如V14，V15等。

我有另一个ListBox，其ItemSource被绑定到ViewModel中的一个属性，该属性依赖于Version DropDown的SelectedValue。

ViewModel看起来像这样：

 class MultiSelectEnvironmentContextControlViewModel: ViewModelBase
    {
        private string selectedVersion;
        private DomainFacade domainFacade;
        private ObservableCollection<string> environments= new ObservableCollection<string>(); 

        public MultiSelectEnvironmentContextControlViewModel()
        {
            domainFacade = ((App) Application.Current).DomainFacade;

        }
        public IEnumerable<string> EnvironmentVersions
        {
            get
            {
                return (domainFacade.GetEnvironmentVersions().Select(v => "Version " + v));
            }
        }    

        public string SelectedVersion
        {
            get { return selectedVersion; }
            set
            {
                selectedVersion = value;
                RaisePropertyChanged("Environments");
            }
        }


                 public ObservableCollection<string> Environments
    {
        get
        {
            environments = (ObservableCollection<string>)(domainFacade.GetEnvironments(SelectedVersion));
            return environments;
        }
    }

    }

我在一个属性中跟踪SelectedVersion，该属性在环境中引发PropertyChanged，这样每当SeelectedVersion发生变化时，环境都应该更新UI。

我面临的问题是，我运行应用程序，我看到正在填充的版本，但ListBox中没有任何内容。

我将UserControl的DataContext设置为UserControl的构造函数中的ViewModel。

以下是我的Control.cs文件的样子：

 public partial class MultiSelectEnvironmentContextControl : UserControl
    {            
        private static MultiSelectEnvironmentContextControlViewModel dataContext = new MultiSelectEnvironmentContextControlViewModel();

        public MultiSelectEnvironmentContextControl()
        {
            InitializeComponent();
            this.DataContext = dataContext;
           dataContext.SelectedVersion = (string)this.ComboBoxVersions.SelectedItem;

        }              

        private void ComboBoxVersions_OnSelectionChanged(object sender, SelectionChangedEventArgs e)
        {
          dataContext.SelectedVersion = ((ComboBox) sender).SelectedValue.ToString();              
        }
}

这是XAML：

    <ComboBox Grid.Column="0" Grid.Row="0" x:Name="ComboBoxVersions" SelectedIndex="0" Margin="10" SelectionChanged="ComboBoxVersions_OnSelectionChanged" ItemsSource="{Binding EnvironmentVersions}">
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding}" />
            </DataTemplate>
        </ComboBox.ItemTemplate>
    </ComboBox>

    <StackPanel Orientation="Horizontal" Grid.Column="1" Grid.Row="0" Margin="10">
        <TextBlock VerticalAlignment="Center" Margin="0,0,10,0">Tests to be run for:</TextBlock>
        <ComboBox  Name="ComboBoxFileTypeSelector" ItemsSource="{Binding AvailableValidationTypes}" DisplayMemberPath="Key" SelectedValuePath="Value" SelectedIndex="0">
        </ComboBox>
    </StackPanel>

    <ListBox x:Name="ListBoxEnvironments" Grid.Column="0" Grid.Row="1" Height="300" Grid.ColumnSpan="2" HorizontalAlignment="Stretch" Margin="10" SelectionMode="Multiple" ItemsSource="{Binding Environments}">
        <ListBox.ItemsPanel>
            <ItemsPanelTemplate>
                <WrapPanel Orientation="Horizontal" HorizontalAlignment="Left" Width="800" >
                </WrapPanel>
            </ItemsPanelTemplate>
        </ListBox.ItemsPanel>
        <ListBox.ItemTemplate>
            <DataTemplate>
                <CheckBox x:Name="CheckBoxEnvironment" Content="{Binding}" IsChecked="{Binding RelativeSource={RelativeSource AncestorType={x:Type ListBoxItem}}, Path=IsSelected}" Margin="5">
                </CheckBox>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

Answer 1

我认为这是因为SelectedVersion具有“版本1”，“版本2”等值，但您的方法DomainFacade.GetEnvironments(string version)需要“1”，“2”等值。

我会像这样编写你的viewmodel：

public class MultiSelectEnvironmentContextControlViewModel : ViewModelBase
{
    private string selectedVersion;
    private DomainFacade domainFacade;
    private IEnumerable<string> environments;

    public MultiSelectEnvironmentContextControlViewModel()
    {
        domainFacade = ((App)Application.Current).DomainFacade;
        EnvironmentVersions = domainFacade.GetEnvironmentVersions();
    }

    public IEnumerable<string> EnvironmentVersions { get; private set; }

    public string SelectedVersion
    {
        get { return selectedVersion; }
        set
        {
            selectedVersion = value;
            RaisePropertyChanged("SelectedVersion");
            Environments = domainFacade.GetEnvironments(SelectedVersion);
        }
    }

    public IEnumerable<string> Environments
    {
        get { return environments; }
        set
        {
            environments = value;
            RaisePropertyChanged("Environments");
        }
    }
}

}

并应用于视图中环境版本的格式化：

<ComboBox SelectedItem="{Binding SelectedVersion}"
          ItemsSource="{Binding EnvironmentVersions}"
          ItemStringFormat="Version: {0}" />

在使用MVVM时，绑定不适用于ListBox

1 个答案: