命令绑定在带有棱镜的 WPF 中不起作用

Question

使用 Prism 库的 WPF MVVM 模式中的事件绑定不适用于子用户控件中的按钮。

我有一个基本视图PreparationMockView，其中有一个内容控件，它是一个子视图LeftBarPrepMockView。现在单击LeftBarPrepMockView 中的按钮时，不会触发SelectedTaskCommand。

下面是父视图和子视图以及各自的视图模型。

• 父视图：

   <UserControl x:Class="PreparationMockUp.Views.PreparationMockView"
               xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
               xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
               xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
               xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
               xmlns:mvvm="http://prismlibrary.com/"
               xmlns:preparationMockUp="clr-namespace:PreparationMockUp"
               mvvm:ViewModelLocator.AutoWireViewModel="True"
               mc:Ignorable="d">
       <Grid>
           <Grid.ColumnDefinitions>
               <ColumnDefinition Width="200" />
               <ColumnDefinition Width="*" />
           </Grid.ColumnDefinitions>
           <ContentControl Grid.Row="0" Grid.Column="0" mvvm:RegionManager.RegionName="{x:Static preparationMockUp:PreparationMockUpModule.LeftBarPreparationRegionName}" />
           <TabControl Grid.Row="0" Grid.Column="1" TabStripPlacement ="Left" Background="#f2f2f3">
       <Grid>
   <UserControl>
  

• 子视图：

   <UserControl x:Class="PreparationMockUp.Views.LeftBarPrepMockView"
               xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
               xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
               xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
               xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
               xmlns:mvvm="http://prismlibrary.com/"
               mvvm:ViewModelLocator.AutoWireViewModel="True"
               mc:Ignorable="d">
           <Grid Background="#1a2231">
           <Grid.RowDefinitions>
               <RowDefinition Height="Auto"/>
               <RowDefinition Height="*"/>
           </Grid.RowDefinitions>
           <StackPanel Grid.Row="1">
           <!-- Bind Rows using the default StackPanel for the ItemsPanel -->
               <ItemsControl Name="taskDisplayList" ItemsSource="{Binding TaskList, Mode=TwoWay}">
               <!-- Set the Template for each row to a TextBlock and another ItemsControl -->
                   <ItemsControl.ItemTemplate>
                   <DataTemplate>
                           <Grid Margin="5">
                               <Grid.ColumnDefinitions>
                                   <ColumnDefinition Width="20" />
                                   <ColumnDefinition Width="*" />
                               </Grid.ColumnDefinitions>
                                   <Button Name="SelectTaskButton" Grid.Column="1" Command="{Binding SelectedTaskCommand}" 
                                       CommandParameter="{Binding}" IsEnabled="{Binding IsEnabled, Mode= TwoWay}" 
                                       BorderThickness ="0" HorizontalAlignment="Left" 
                                       Style="{StaticResource TaskButton}"
                                       Content="{Binding Name}">
                               </Button>
                           </Grid>
                   </DataTemplate>
               </ItemsControl.ItemTemplate>
           </ItemsControl>
           </StackPanel>
       </Grid>
   <UserControl>
  

• 视图模型：

   namespace PreparationMockUp.ViewModels
   {
       public class LeftBarPrepMockViewModel : ViewModelBase
       {
           private readonly IEventAggregator _eventAggregator;
           private Tasks tasks;
           readonly string path = ConfigurationManager.AppSettings["ConfigPath"].ToString();
  
           public LeftBarPrepMockViewModel(IEventAggregator ea)
           {
               _eventAggregator = ea;
               _eventAggregator.GetEvent<PubSubEvent<PubSubMessages>>().Subscribe((message) => InsertedCylinder(),
                   ThreadOption.UIThread, true, x => x.Equals(PubSubMessages.InsertedBuildCylinder));
               SelectedTaskCommand = new DelegateCommand(NavigateToSelectedTask);
           }
  
           public ICommand SelectedTaskCommand { get; set; }
  
           private List<Task> _taskList;
           public List<Task> TaskList 
           { 
               get 
               {
                   return _taskList;
               }
               set
               {
                   _taskList = value;
                   OnPropertyChanged(new PropertyChangedEventArgs("TaskList"));
               } 
           }
           private void NavigateToSelectedTask(){ }           
       }
   }
  

Answer 1

您将SelectedTaskCommand 绑定到名为root 的元素，但它在您的代码中不存在。

Command="{Binding SelectedTaskCommand, ElementName=root}"

假设您指的是名为 taskDisplayList 的 ItemsControl。然后您可以使用ElementName 创建绑定，但您仍然需要引用该元素的DataContext 才能绑定到视图模型。否则绑定将搜索控件本身的属性，该属性不存在。

Command="{Binding DataContext.SelectedTaskCommand, ElementName=taskDisplayList}"

另一种方法是使用RelativeSource 绑定LeftBarPrepMockView 用户控件。

Command="{Binding DataContext.SelectedTaskCommand, RelativeSource={RelativeSource AncestorType={x:Type local:LeftBarPrepMockView}}}" 

您当然也可以使用绑定到ItemsControl 或其他控件，而无需ElementName。