我正在使用一个WPF MVVM应用程序，其中TreeView包含在XAML页面中维护的所有静态项目。如何在我的视图模型中知道单击了哪个MenuItem，以便我可以相应地显示相应的页面。
<TreeView Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="MyTreeViewMenu"
VerticalAlignment="Stretch" Width="Auto" Opacity="1"
BorderThickness="1" BorderBrush="Black" Grid.Row="2">
<TreeViewItem Header="Country" Width="Auto" HorizontalAlignment="Stretch"
></TreeViewItem>
<TreeViewItem Header="View Details" Width="Auto" HorizontalAlignment="Stretch" IsEnabled="False">
<TreeViewItem Header="User" />
<TreeViewItem Header="Group" />
<TreeViewItem Header="User Group" />
</TreeViewItem>
</TreeView>
答案 0 :(得分：2)
我认为Selected事件与您案件中click的效果相同。要确定选择了哪个TreeViewItem，您应该添加事件Trigger：
<TreeView Height="Auto" HorizontalAlignment="Stretch" Margin="0" Name="MyTreeViewMenu"
VerticalAlignment="Stretch" Width="Auto" Opacity="1"
BorderThickness="1" BorderBrush="Black" Grid.Row="2">
<TreeViewItem Header="Country" Width="Auto" HorizontalAlignment="Stretch"></TreeViewItem>
<TreeViewItem Header="View Details" Width="Auto" HorizontalAlignment="Stretch" IsEnabled="False">
<TreeViewItem Header="User" />
<TreeViewItem Header="Group" />
<TreeViewItem Header="User Group" />
</TreeViewItem>
<i:Interaction.Triggers>
<i:EventTrigger EventName="SelectedItemChanged">
<i:InvokeCommandAction
Command="{Binding selectItemCommand}"
CommandParameter="{Binding SelectedItem, ElementName=MyTreeViewMenu}"/>
</i:EventTrigger>
</i:Interaction.Triggers>
</TreeView>
因此，您可以使用并确定传递给Command的参数选择的项目。
ViewModel应该是这样的：
private ICommand _selectItemCommand;
public ICommand selectItemCommand
{
get
{
return _selectItemCommand ?? (_selectItemCommand = new RelayCommand(param => this.LoadPage(param)));
}
}
private void LoadPage(object selectedMenuItem)
{
...
}
答案 1 :(得分：2)
查看MSDN上的TreeView.SelectedItem Property页面。
您可以直接绑定到TreeView.SelectedItem属性：
<TreeView ItemsSource="{Binding Items}" SelectedItem="{Binding Item, Mode=OneWay}" />
请注意，TreeView.SelectedItem属性只是只读属性，因此必须使用OneWay绑定...这意味着您无法在视图中设置所选项目模型。为此，您需要使用Attached Property创建自己的双向选定项属性。
编辑＆gt;＆gt;＆gt;
我的道歉@ Scroog1，我通常使用AttachedProperty来做到这一点。你是对的，即使使用OneWay绑定，使用此方法也会出错。不幸的是，我的AttachedProperty代码很长，但还有另一种方法可以做到这一点。
我不一定会推荐这个，因为将UI属性放入数据对象永远不是一个好主意，但如果向数据对象添加IsSelected属性，则可以将其直接绑定到数据对象TreeViewItem.IsSelected财产：
<TreeView ItemsSource="Items" HorizontalAlignment="Stretch" ... Name="MyTreeViewMenu">
<TreeView.ItemContainerStyle>
<Style TargetType="{x:Type TreeViewItem}">
<Setter Property="IsSelected" Value="{Binding IsSelected}" />
</Style>
</TreeView.ItemContainerStyle>
</TreeView>
我刚刚在StackOverflow上的WPF MVVM TreeView SelectedItem帖子中搜索并找到了一个“更全面”的答案。
或者，还有另外一种方法......您也可以使用TreeView.SelectedValue和TreeView.SelectedValuePath属性。基本思想是将TreeView.SelectedValuePath属性设置为数据对象上属性的名称。选择项目后，TreeView.SelectedValue属性将设置为所选数据项的该属性的值。您可以在MSDN的How to: Use SelectedValue, SelectedValuePath, and SelectedItem页面上找到有关此方法的更多信息。如果您拥有可识别的唯一属性（如某种标识符），则通常效果最佳。此代码示例来自MSDN：
<TreeView ItemsSource="{Binding Source={StaticResource myEmployeeData},
XPath=EmployeeInfo}" Name="myTreeView" SelectedValuePath="EmployeeNumber" />
<TextBlock Margin="10">SelectedValuePath: </TextBlock>
<TextBlock Margin="10,0,0,0" Text="{Binding ElementName=myTreeView,
Path=SelectedValuePath}" Foreground="Blue"/>
<TextBlock Margin="10">SelectedValue: </TextBlock>
<TextBlock Margin="10,0,0,0" Text="{Binding ElementName=myTreeView,
Path=SelectedValue}" Foreground="Blue"/>
答案 2 :(得分：0)
除了绑定到TreeView.SelectedItem属性：
使用MVVM时，它帮助我不再考虑UI中的事件，并开始考虑UI中的状态。
您可以将ViewModel绑定到View的属性。因此，一般来说，我尝试将SelectedItem绑定到ViewModel上的属性，以便ViewModel知道所选内容。
以同样的方式，您可以向显示的名为Selected的ViewModel项添加属性，并将此属性绑定到View中的复选框。这样，您就可以在ViewModel中轻松启用多项选择和访问所选项目。
答案 3 :(得分：0)
为了完整性，这里是附加属性和TreeView子类选项：
附加财产选项
public static class TreeViewSelectedItemHelper
{
public static readonly DependencyProperty BindableSelectedItemProperty
= DependencyProperty.RegisterAttached(
"BindableSelectedItem",
typeof (object),
typeof (TreeViewSelectedItemHelper),
new FrameworkPropertyMetadata(false,
OnSelectedItemPropertyChanged)
{
BindsTwoWayByDefault = true
});
public static object GetBindableSelectedItem(TreeView treeView)
{
return treeView.GetValue(BindableSelectedItemProperty);
}
public static void SetBindableSelectedItem(
TreeView treeView,
object selectedItem)
{
treeView.SetValue(BindableSelectedItemProperty, selectedItem);
}
private static void OnSelectedItemPropertyChanged(
DependencyObject sender,
DependencyPropertyChangedEventArgs args)
{
var treeView = sender as TreeView;
if (treeView == null) return;
SetBindableSelectedItem(treeView, args.NewValue);
treeView.SelectedItemChanged -= HandleSelectedItemChanged;
treeView.SelectedItemChanged += HandleSelectedItemChanged;
if (args.OldValue != args.NewValue)
SetSelected(treeView, args.NewValue);
}
private static void SetSelected(ItemsControl treeViewItem,
object itemToSelect)
{
foreach (var item in treeViewItem.Items)
{
var generator = treeViewItem.ItemContainerGenerator;
var child = (TreeViewItem) generator.ContainerFromItem(item);
if (child == null) continue;
child.IsSelected = (item == itemToSelect);
if (child.HasItems) SetSelected(child, itemToSelect);
}
}
private static void HandleSelectedItemChanged(
object sender,
RoutedPropertyChangedEventArgs<object> args)
{
if (args.NewValue is TreeViewItem) return;
var treeView = sender as TreeView;
if (treeView == null) return;
var binding = BindingOperations.GetBindingExpression(treeView,
BindableSelectedItemProperty);
if (binding == null) return;
var propertyName = binding.ParentBinding.Path.Path;
var property = binding.DataItem.GetType().GetProperty(propertyName);
if (property != null)
property.SetValue(binding.DataItem, treeView.SelectedItem, null);
}
}
子类选项
public class BindableTreeView : TreeView
{
public BindableTreeView()
{
SelectedItemChanged += HandleSelectedItemChanged;
}
public static readonly DependencyProperty BindableSelectedItemProperty =
DependencyProperty.Register(
"BindableSelectedItem",
typeof (object),
typeof (BindableTreeView),
new FrameworkPropertyMetadata(
default(object),
OnBindableSelectedItemChanged) {BindsTwoWayByDefault = true});
public object BindableSelectedItem
{
get { return GetValue(BindableSelectedItemProperty); }
set { SetValue(BindableSelectedItemProperty, value); }
}
private static void OnBindableSelectedItemChanged(
DependencyObject d,
DependencyPropertyChangedEventArgs e)
{
var treeView = d as TreeView;
if (treeView != null) SetSelected(treeView, e.NewValue);
}
private static void SetSelected(ItemsControl treeViewItem,
object itemToSelect)
{
foreach (var item in treeViewItem.Items)
{
var generator = treeViewItem.ItemContainerGenerator;
var child = (TreeViewItem) generator.ContainerFromItem(item);
if (child == null) continue;
child.IsSelected = (item == itemToSelect);
if (child.HasItems) SetSelected(child, itemToSelect);
}
}
private void HandleSelectedItemChanged(
object sender,
RoutedPropertyChangedEventArgs<object> e)
{
SetValue(BindableSelectedItemProperty, SelectedItem);
}
}