ListBox SelectedItem始終為null

Question

當我單擊ListBox中的項目時，它始終返回null。 當然我的ListBox已經裝滿了:-)
我的XAML代碼：

<Window x:Class="WpfTimeClock.AdminWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:local="clr-namespace:WpfTimeClock"
    mc:Ignorable="d"
    ResizeMode="CanMinimize"
    Title="AdminWindow" Height="527" Width="750">
<Grid>
    <ListBox x:Name="listBoxUsers" HorizontalAlignment="Left" Height="250" VerticalAlignment="Top" Width="200" Margin="10,10,0,0"/>
</Grid>
</Window>

我的C＃代碼：

TimeClockRepository<User> repUser = new TimeClockRepository<User>();

public AdminWindow()
{
    InitializeComponent();
    Loaded += AdminWindow_Loaded;
    listBoxUsers.PreviewMouseLeftButtonDown += ListBoxUsers_PreviewMouseLeftButtonDown;
}

private void ListBoxUsers_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    var item = sender as ListBoxItem;
    if (item != null && item.IsSelected)
    {
        // why is sender always null??
    }
}

private void AdminWindow_Loaded(object sender, RoutedEventArgs e)
{
    listBoxUsers.ItemsSource = repUser.Get().ToList();
    listBoxUsers.DisplayMemberPath = "UserName";
}

當我單擊它時，我的sender項目始終為空。 問題是什么？ 謝謝你的幫助！

Answer 1

您應該處理ListViewItem ，而不是ListBox 。 只需在ListView.ItemContainerStyle為ListViewItem創建處理程序：

XAML：

<ListView ItemsSource={Binding YourItems}>
    <ListView.View>
        <GridView>
            <!-- Declare a GridViewColumn for each property -->
        </GridView>
    </ListView.View>
    <ListView.ItemContainerStyle>
        <Style TargetType="ListViewItem">
            <EventSetter Event="PreviewMouseLeftButtonDown" Handler="ListViewItem_PreviewMouseLeftButtonDown" />
        </Style>
    </ListView.ItemContainerStyle>
</ListView>

后台代碼：

private void ListViewItem_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
    var item = sender as ListViewItem;
    if (item != null && item.IsSelected)
    {
        //Do your actions
    }
}

Answer 2

您應該改用SelectionChanged事件。

this.listBoxUsers.SelectionChanged += ListBoxUsers_SelectionChanged;

private void ListBoxUsers_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    // do your things with listBoxUsers.SelectedItem
    // If you want to click same item more than once, set SelectedIndex to -1 after use it.
}