WPF ListBoxItem MVVM 中的 SelectedItem 问题

Question

我是 WPF 的新手，正在尝试按照 MVVM 设计模式进行设计。我的问题是，当用户在 ListBox 中选择此项时，我无法获取所选项目。感谢您的帮助，谢谢。我已经删除了一些不需要的方法中的代码。

抱歉，我应该添加名为：lbPositionAttributeMasters 的列表框不起作用。

XAML:

<Grid>
    <StackPanel />
    <ListBox x:Name="lbPositionAttributeMasters" ItemsSource="{Binding PositionAttributeMasterCollection}" SelectedItem="{Binding SelectedAttributeMaster, Mode=TwoWay}" Margin="0,10,280,10">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding PositionAttributeMasterDescription}"></TextBlock>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

    <ListBox x:Name="lbPositionAttributesForMaster" ItemsSource="{Binding PositionAttributesCollection}" Margin="270,10,10,10">
        <ListBox.ItemTemplate>
            <DataTemplate>
                <TextBlock Text="{Binding PositionAttributeDescription}"></TextBlock>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>

</Grid>

视图模型：

public event PropertyChangedEventHandler PropertyChanged;
    private ObservableCollection<PositionAttributes> _positionAttributeMasterCollection;
    private ObservableCollection<PositionAttributes> _positionAttributeCollection;
    private IList<PositionAttributes> _positionAttributeMasterDescription;
    private IList<PositionAttributes> _positionAttributeDescription;
    private PositionAttributes _selectedAttributeMaster;
    public PositionAttributesViewModel()
    {

    }

    private void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
        }
    }

    public ObservableCollection<PositionAttributes> PositionAttributeMasterCollection
    {
        get { return _positionAttributeMasterCollection;}
        set
        {
            _positionAttributeMasterCollection = value;
            OnPropertyChanged("PositionAttributeMasterCollection");
        }
    }

    public ObservableCollection<PositionAttributes> PositionAttributeCollection
    {
        get { return _positionAttributeCollection; }
        set
        {
            _positionAttributeCollection = value;
            OnPropertyChanged("PositionAttributeCollection");
        }
    }

    public IList<PositionAttributes> PositionAttributeMasterDescription
    {
        get { return _positionAttributeMasterDescription; }
        set
        {
            _positionAttributeMasterDescription = value;
            OnPropertyChanged("PositionAttributeMasterDescription");
        }
    }

    public PositionAttributes SelectedAttributeMaster
    {
        get{ return _selectedAttributeMaster; }

        set
        {
            _selectedAttributeMaster = value;
            OnPropertyChanged("SelectedAttributeMaster");
        }

    }

    public IList<PositionAttributes> PositionAttributeDescription
    {
        get { return _positionAttributeDescription; }
        set
        {
            _positionAttributeDescription = value;
            OnPropertyChanged("PositionAttributeDescription");
        }
    }

    /// <summary>
    /// Gets all Attribute Masters and Sub Attribute Masters
    /// </summary>
    /// <returns></returns>
    public ObservableCollection<PositionAttributes> GetPositionAttributeMasters()
    {

        foreach(var item in listofpositionAttributes)//Add to observable collection
        {
            PositionAttributeMasterCollection.Add(item);
        }

        return PositionAttributeMasterCollection;
    }


            foreach (var item in positionAttributesInMaster)//Add to observable collection
            {
                PositionAttributeCollection.Add(item);
            }
        }

        return PositionAttributeCollection;
    }

}

Answer 1

第一步。在您的视图模型中添加中继命令

    /// <summary>
    /// Command which is fired when a list view item is selected in   the    main window 
    /// </summary>
    public RelayCommand SelectionChangedCmd { get; private set; }

    /// <summary>
    /// The listview item selected from the collection.
    /// </summary>
    public Feature SelectedAttributedMaster  { get; set; }

在您的视图模型的构造函数中：

      public PositionAttributesViewModel()
      {
        PositionAttributeMasterCollection = new    
                ObservableCollection<PositionAttributes >();

        SelectionChangedCmd = new RelayCommand(() =>        
              PositionAttributesSelectionChanged(), () => true);


     }


 //implement what you want to do on selection 
  private void PositionAttributesSelectionChanged()
  {
      if(PositionAttributeMasterCollection !=null &&     
       SelectedAttributedMaster !=null)
        {
           PositionAttributes feature = SelectedAttributedMaster  as     
           PositionAttributes 
           //Update the window whenever we select a new feature.
           Dispatcher.CurrentDispatcher.DynamicInvoke(delegate()
           {
                //further implementation

           });

        }
  }

在您的 XAML 中添加引用和其余代码。

   <Window x:Class="Something.MainWindow" 
        xmlns:i="clr-namespace:System.Windows.Interactivity;  assembly=System.Windows.Interactivity"
        xmlns:cmd="clr-namespace:GalaSoft.MvvmLight.Command;assembly=GalaSoft.MvvmLight.Extras.WPF4">

  <ListBox x:Name="lbPositionAttributeMasters" ItemsSource="{Binding PositionAttributeMasterCollection}" SelectedItem="{Binding SelectedAttributeMaster}" Margin="0,10,280,10">
    <ListBox.ItemTemplate>
        <DataTemplate>
            <TextBlock Text="{Binding PositionAttributeMasterDescription}"></TextBlock>
        </DataTemplate>
    </ListBox.ItemTemplate>
      <i:Interaction.Triggers>
                    <i:EventTrigger EventName="SelectionChanged">
                        <i:InvokeCommandAction Command="{Binding SelectionChangedCmd}"
                         CommandParameter="{Binding}" />
                    </i:EventTrigger>
       </i:Interaction.Triggers>
</ListBox>

Answer 2

您提供的代码按预期工作。你在评论中描述的是，在调试期间你看到 {ClientRatesWPF.Model.PositionAttributes} 作为一个值被设置为 SelectedAttributeMaster.
这是完全正确的，因为调试器不知道如何向您显示更有意义的内容。你可以做两件事：

1) 将 DebuggerDisplay 属性应用到您的 class:

[DebuggerDisplay("Description = {PositionAttributeMasterDescription}")]
public class PositionAttributes
{        
    public string PositionAttributeMasterDescription { get; set; }
}

2) 使用 Visual Studio 调试器向您显示更多信息：

WPF ListBoxItem MVVM 中的 SelectedItem 问题

SelectedItem issue in WPF ListBoxItem MVVM

c#

wpf

xaml

mvvm