如何检索在WPF-treeview中选择的项?我想在XAML中这样做,因为我想绑定它。

您可能认为它是SelectedItem,但显然它不存在是只读的,因此不可用。

这就是我想做的:

<TreeView ItemsSource="{Binding Path=Model.Clusters}" 
            ItemTemplate="{StaticResource ClusterTemplate}"
            SelectedItem="{Binding Path=Model.SelectedCluster}" />

我想将SelectedItem绑定到我的Model上的一个属性。

但这给了我一个错误:

“SelectedItem”属性是只读的,不能从标记中设置。

编辑: 这就是我解决这个问题的方法:

<TreeView
          ItemsSource="{Binding Path=Model.Clusters}" 
          ItemTemplate="{StaticResource HoofdCLusterTemplate}"
          SelectedItemChanged="TreeView_OnSelectedItemChanged" />

在我的xaml的代码背后文件:

private void TreeView_OnSelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e)
{
    Model.SelectedCluster = (Cluster)e.NewValue;
}

当前回答

这可以以一种“更好”的方式完成,只使用绑定和GalaSoft MVVM Light库的EventToCommand。在您的VM中添加一个命令,当所选项目发生变化时将调用该命令,并初始化该命令以执行任何必要的操作。在这个例子中,我使用了一个RelayCommand,只设置SelectedCluster属性。

public class ViewModel
{
    public ViewModel()
    {
        SelectedClusterChanged = new RelayCommand<Cluster>( c => SelectedCluster = c );
    }

    public RelayCommand<Cluster> SelectedClusterChanged { get; private set; } 

    public Cluster SelectedCluster { get; private set; }
}

然后在xaml中添加EventToCommand行为。使用混合非常简单。

<TreeView
      x:Name="lstClusters"
      ItemsSource="{Binding Path=Model.Clusters}" 
      ItemTemplate="{StaticResource HoofdCLusterTemplate}">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="SelectedItemChanged">
            <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding SelectedClusterChanged}" CommandParameter="{Binding ElementName=lstClusters,Path=SelectedValue}"/>
        </i:EventTrigger>
    </i:Interaction.Triggers>
</TreeView>

其他回答

当点击某些项目列表时,你会在“选定”属性中获得数据。 视图模型:

public class ShellViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler PropertyChanged;

    protected void NotifyPropertyChanged(String info)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(info));
        }
    }

    private ObservableCollection<Books> _books;

    private List<Books> bookList = new List<Books>();

    public ObservableCollection<Books> Books
    {
        get { return _books; }
        set { _books = value; NotifyPropertyChanged("Books"); }
    }

    private Books books;

    public Books Selected
    {
        get { return books; }
        set { books = value; }
    }


    public ShellViewModel()
    {
        bookList = new List<Books>()
        {
            new Books{BookName = "Harry Poter",Price ="15$"},
            new Books{BookName = "Harry Poter 2 ",Price ="14.95$"},
            new Books{BookName = "Harry Poter 3",Price ="18.50$"},
            new Books{BookName = "Harry Poter 4",Price ="32.90$"},
        };

        Books = new ObservableCollection<Books>(bookList);
    }
}

public class Books
{
    public string BookName { get; set; }
    public string Price { get; set; }
}

XAML:

 <ListView x:Name="lst" Grid.Row="2" ItemsSource="{Binding Books}" SelectedItem="{Binding Selected}">
        <ListView.View>
            <GridView >
                <GridViewColumn Header="Name" DisplayMemberBinding="{Binding BookName}"  />
                <GridViewColumn Header="Price" Width="100" DisplayMemberBinding="{Binding Price}"/>
            </GridView>
        </ListView.View>
    </ListView>

这可以以一种“更好”的方式完成,只使用绑定和GalaSoft MVVM Light库的EventToCommand。在您的VM中添加一个命令,当所选项目发生变化时将调用该命令,并初始化该命令以执行任何必要的操作。在这个例子中,我使用了一个RelayCommand,只设置SelectedCluster属性。

public class ViewModel
{
    public ViewModel()
    {
        SelectedClusterChanged = new RelayCommand<Cluster>( c => SelectedCluster = c );
    }

    public RelayCommand<Cluster> SelectedClusterChanged { get; private set; } 

    public Cluster SelectedCluster { get; private set; }
}

然后在xaml中添加EventToCommand行为。使用混合非常简单。

<TreeView
      x:Name="lstClusters"
      ItemsSource="{Binding Path=Model.Clusters}" 
      ItemTemplate="{StaticResource HoofdCLusterTemplate}">
    <i:Interaction.Triggers>
        <i:EventTrigger EventName="SelectedItemChanged">
            <GalaSoft_MvvmLight_Command:EventToCommand Command="{Binding SelectedClusterChanged}" CommandParameter="{Binding ElementName=lstClusters,Path=SelectedValue}"/>
        </i:EventTrigger>
    </i:Interaction.Triggers>
</TreeView>

走吧

... 是一个更好的答案,但没有提到一种在ViewModel中获取/设置SelectedItem的方法。

添加一个IsSelected布尔属性到ItemViewModel,并在TreeViewItem的样式设置器中绑定到它。 在ViewModel中添加SelectedItem属性,作为TreeView的DataContext。这是上面解决方案中缺少的部分。

    ' ItemVM...
    Public Property IsSelected As Boolean
        Get
            Return _func.SelectedNode Is Me
        End Get
        Set(value As Boolean)
            If IsSelected  value Then
                _func.SelectedNode = If(value, Me, Nothing)
            End If
            RaisePropertyChange()
        End Set
    End Property
    ' TreeVM...
    Public Property SelectedItem As ItemVM
        Get
            Return _selectedItem
        End Get
        Set(value As ItemVM)
            If _selectedItem Is value Then
                Return
            End If
            Dim prev = _selectedItem
            _selectedItem = value
            If prev IsNot Nothing Then
                prev.IsSelected = False
            End If
            If _selectedItem IsNot Nothing Then
                _selectedItem.IsSelected = True
            End If
        End Set
    End Property
<TreeView ItemsSource="{Binding Path=TreeVM}" 
          BorderBrush="Transparent">
    <TreeView.ItemContainerStyle>
        <Style TargetType="TreeViewItem">
            <Setter Property="IsExpanded" Value="{Binding IsExpanded}"/>
            <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}"/>
        </Style>
    </TreeView.ItemContainerStyle>
    <TreeView.ItemTemplate>
        <HierarchicalDataTemplate ItemsSource="{Binding Children}">
            <TextBlock Text="{Binding Name}"/>
        </HierarchicalDataTemplate>
    </TreeView.ItemTemplate>
</TreeView>

(让我们都同意,TreeView在这个问题上显然是行不通的。绑定到SelectedItem是显而易见的。叹息)

我需要解决方案来正确地与TreeViewItem的IsSelected属性交互,所以这是我是如何做到的:

// the Type CustomThing needs to implement IsSelected with notification
// for this to work.
public class CustomTreeView : TreeView
{
    public CustomThing SelectedCustomThing
    {
        get
        {
            return (CustomThing)GetValue(SelectedNode_Property);
        }
        set
        {
            SetValue(SelectedNode_Property, value);
            if(value != null) value.IsSelected = true;
        }
    }

    public static DependencyProperty SelectedNode_Property =
        DependencyProperty.Register(
            "SelectedCustomThing",
            typeof(CustomThing),
            typeof(CustomTreeView),
            new FrameworkPropertyMetadata(
                null,
                FrameworkPropertyMetadataOptions.None,
                SelectedNodeChanged));

    public CustomTreeView(): base()
    {
        this.SelectedItemChanged += new RoutedPropertyChangedEventHandler<object>(SelectedItemChanged_CustomHandler);
    }

    void SelectedItemChanged_CustomHandler(object sender, RoutedPropertyChangedEventArgs<object> e)
    {
        SetValue(SelectedNode_Property, SelectedItem);
    }

    private static void SelectedNodeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
        var treeView = d as CustomTreeView;
        var newNode = e.NewValue as CustomThing;

        treeView.SelectedCustomThing = (CustomThing)e.NewValue;
    }
}

用这个XAML:

<local:CustonTreeView ItemsSource="{Binding TreeRoot}" 
    SelectedCustomThing="{Binding SelectedNode,Mode=TwoWay}">
    <TreeView.ItemContainerStyle>
        <Style TargetType="TreeViewItem">
            <Setter Property="IsSelected" Value="{Binding IsSelected, Mode=TwoWay}" />
        </Style>
    </TreeView.ItemContainerStyle>
</local:CustonTreeView>

我提出了这个解决方案(我认为这是最简单的,并且没有内存泄漏),它非常适合从视图的选定项更新ViewModel的选定项。

请注意,从ViewModel中更改所选项不会更新视图中的所选项。

public class TreeViewEx : TreeView
{
    public static readonly DependencyProperty SelectedItemExProperty = DependencyProperty.Register("SelectedItemEx", typeof(object), typeof(TreeViewEx), new FrameworkPropertyMetadata(default(object))
    {
        BindsTwoWayByDefault = true // Required in order to avoid setting the "BindingMode" from the XAML
    });

    public object SelectedItemEx
    {
        get => GetValue(SelectedItemExProperty);
        set => SetValue(SelectedItemExProperty, value);
    }

    protected override void OnSelectedItemChanged(RoutedPropertyChangedEventArgs<object> e)
    {
        SelectedItemEx = e.NewValue;
    }
}

XAML usage

<l:TreeViewEx ItemsSource="{Binding Path=Items}" SelectedItemEx="{Binding Path=SelectedItem}" >