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;
}
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}" >
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>
我给你带来了我的解决方案，它具有以下特点:
支持2种绑定方式
自动更新TreeViewItemIsSelected属性(根据SelectedItem)
没有TreeView子类
绑定到ViewModel的项可以是任何类型(甚至是null)
1/在你的CS中粘贴以下代码:
public class BindableSelectedItem
{
public static readonly DependencyProperty SelectedItemProperty = DependencyProperty.RegisterAttached(
"SelectedItem", typeof(object), typeof(BindableSelectedItem), new PropertyMetadata(default(object), OnSelectedItemPropertyChangedCallback));
private static void OnSelectedItemPropertyChangedCallback(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
var treeView = d as TreeView;
if (treeView != null)
{
BrowseTreeViewItems(treeView, tvi =>
{
tvi.IsSelected = tvi.DataContext == e.NewValue;
});
}
else
{
throw new Exception("Attached property supports only TreeView");
}
}
public static void SetSelectedItem(DependencyObject element, object value)
{
element.SetValue(SelectedItemProperty, value);
}
public static object GetSelectedItem(DependencyObject element)
{
return element.GetValue(SelectedItemProperty);
}
public static void BrowseTreeViewItems(TreeView treeView, Action<TreeViewItem> onBrowsedTreeViewItem)
{
var collectionsToVisit = new System.Collections.Generic.List<Tuple<ItemContainerGenerator, ItemCollection>> { new Tuple<ItemContainerGenerator, ItemCollection>(treeView.ItemContainerGenerator, treeView.Items) };
var collectionIndex = 0;
while (collectionIndex < collectionsToVisit.Count)
{
var itemContainerGenerator = collectionsToVisit[collectionIndex].Item1;
var itemCollection = collectionsToVisit[collectionIndex].Item2;
for (var i = 0; i < itemCollection.Count; i++)
{
var tvi = itemContainerGenerator.ContainerFromIndex(i) as TreeViewItem;
if (tvi == null)
{
continue;
}
if (tvi.ItemContainerGenerator.Status == System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated)
{
collectionsToVisit.Add(new Tuple<ItemContainerGenerator, ItemCollection>(tvi.ItemContainerGenerator, tvi.Items));
}
onBrowsedTreeViewItem(tvi);
}
collectionIndex++;
}
}
}
2/在XAML文件中使用的例子
<TreeView myNS:BindableSelectedItem.SelectedItem="{Binding Path=SelectedItem, Mode=TwoWay}" />
