使用 XAML 数据绑定获取单击的项对象

Question

我正在将我的ListBox绑定到一个项目集合，该集合包含我的Item类的实例。

此部分按预期工作。我遇到的问题是访问单击的列表框项item实例。我已经包含了完整的示例和相关的 XAML。

我还包含一个示例，说明我希望如何在listBoxItems_PreviewMouseDown事件处理程序中访问Item实例。

我假设我错过了一些明显的东西，但是当我单击一个项目时代码崩溃。我是否缺少另一个将所有这些粘合在一起的绑定？

谢谢

代码隐藏：

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Threading;
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
// Item class
internal class Item : INotifyPropertyChanged
{
public Item(string name = null)
{
this.Name = name;
}
public string Name { get; set; }
public string ImagePath { get; set; }
public string SomeString { get; set; }
public int SomeInt { get; set; }
public event PropertyChangedEventHandler PropertyChanged;
private void NotifyPropertyChanged(String propertyName)
{
if (PropertyChanged != null)
{
PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
}
}
}
// Item collection
ObservableCollection<Item> ItemsCollection;
public MainWindow()
{
InitializeComponent();
// Initialize the items collection
this.ItemsCollection = new ObservableCollection<Item>();
for (int i = 0; i < 5; i ++)
{
Dispatcher.Invoke(new Action(() =>
{
Item newItem = new Item
{
Name = "test " + i,
ImagePath = @"Images" + i + ".jpg",
SomeString = "example" + i,
SomeInt = i,
};
// Add the new item to the collection
this.ItemsCollection.Add(newItem);
}), DispatcherPriority.Background);
}
// Set the items source
this.listBoxItems.ItemsSource = this.ItemsCollection;
}
// Handle mouse down events on listbox items
private void listBoxItems_PreviewMouseDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
// Ideally, i'd like to do something like this
Item item = sender as Item;
// So then I could do for example
Console.WriteLine(@"Clicked item SomeString: {0}, SomeInt {1}", item.SomeString, item.SomeInt);
}
}
}

XAML：

<userControls:MyListBox x:Name="ItemsListBox" ItemsSource="{Binding ItemsCollection}" PreviewMouseDown="listBoxItems_PreviewMouseDown">
<ListBox.ItemTemplate>
<DataTemplate>
<VirtualizingStackPanel>
<Image Source="{Binding ImagePath}" Width="200" Height="100"/>
<TextBlock Text="{Binding Name}" />
</VirtualizingStackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
</userControls:MyListBox>

Answer 1

除了接受的答案外，您也可以将PreviewMouseDown事件直接绑定到ListBoxItem。

在这种情况下，XAML可以是(强调添加的<ListBox.ItemContainerStyle>节点)：

<userControls:MyListBox x:Name="ItemsListBox" ItemsSource="{Binding ItemsCollection}" PreviewMouseDown="listBoxItems_PreviewMouseDown">
<ListBox.ItemTemplate>
<DataTemplate>
<VirtualizingStackPanel>
<Image Source="{Binding ImagePath}" Width="200" Height="100"/>
<TextBlock Text="{Binding Name}" />
</VirtualizingStackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
<ListBox.ItemContainerStyle>
<Style TargetType="{x:Type ListBoxItem}">
<EventSetter Event="PreviewMouseDown" Handler="listBoxItems_PreviewMouseDown" />
</Style>
</ListBox.ItemContainerStyle>
</userControls:MyListBox>

和处理程序：

// Handle mouse down events on listbox items
private void listBoxItems_PreviewMouseDown(object sender, System.Windows.Input.MouseButtonEventArgs e)
{
// Ideally, i'd like to do something like this
Item item = (sender as ListBoxItem).DataContext as Item;
// So then I could do for example
Console.WriteLine(@"Clicked item SomeString: {0}, SomeInt {1}", item.SomeString, item.SomeInt);
}

Answer 2

您可以获取事件的OriginalSource并检查其DataContext：

var item = (e.OriginalSource as FrameworkElement)?.DataContext as Item;
if (item != null) { /* Do something with item... */ }