WPF ListBox 多项选择不会在模型上引发 SelectedItem

Question

我的列表框有问题我已将 ListBox selection 模式设置为 Multiple 问题是 Selected Item 只触发一次，当我 select 其他项目时，它不会更改视图模型中的 SelectedItem。我确定它 selection 它们是因为我在 selected 时将属性绑定为 true，但 selected 项目不会更新。例如：可以说我有以下列表框：一种乙 C 选择 A -> ViewModel 将 selectedItem 更新为 A 选择 B -> ViewModel 不更新 SelectedItem 但我可以看到 B 是 selected 当我 deselect A 时，ViewModel 将 SelectedItem 更新为 null 有人已经遇到这个问题了吗？我的主要目标是让我的 SelectedItem 更新到我选择的那个他是我的视图代码：

<ListBox HorizontalAlignment="Center"  ItemsSource="{Binding AvailableDagrVMEs}"
                     SelectedItem="{Binding SelectedDagrVME}"
                     SelectionMode="Multiple"
                     VirtualizingStackPanel.IsVirtualizing="False"
                     ScrollViewer.HorizontalScrollBarVisibility="Auto" Padding="0" Margin="0" ScrollViewer.VerticalScrollBarVisibility="Hidden" ScrollViewer.PanningMode="HorizontalOnly"
                     Background="Transparent"
                     BorderThickness="0">
                    <ListBox.ItemsPanel>
                        <ItemsPanelTemplate>
                            <UniformGrid Rows="1"/>
                        </ItemsPanelTemplate>
                    </ListBox.ItemsPanel>
                    <ListBox.ItemContainerStyle>
                        <Style TargetType="{x:Type ListBoxItem}">
                            <Setter Property="IsSelected" Value="{Binding Taken, Mode=TwoWay}"/>
                        </Style>
                    </ListBox.ItemContainerStyle>
                    <ListBox.ItemTemplate>
                        <DataTemplate>
                            <DockPanel>
                                <Image Source="{Binding Icon , Converter={StaticResource BitmapToImageSourceConverter}}"/>
                            </DockPanel>
                        </DataTemplate>
                    </ListBox.ItemTemplate>
                </ListBox>

和视图模型：

        public BaseVME SelectedDagrVME
    {
        get { return selectedDagrVME; }
        set
        {
            if (selectedDagrVME != value)
            {
                Set("SelectedDagrVME", ref selectedDagrVME, value);
            }
        }
    }

我试过：TwoWay binding/UpdateTriggerSource

Answer 1

由于您有 Multiple 个选择，因此 SelectedItem 将始终是您选择的第一个。要获得最后选择的项目，您必须注册 SelectionChanged 活动并访问 SelectedItems 属性，其中包含您选择的所有项目。你可以用一个行为来实现它，因为你可以重用它。

行为：

public class ListBoxSelection : Behavior<ListBox>
{
    public static readonly DependencyProperty LastSelectedProperty = DependencyProperty.Register(nameof(LastSelected), typeof(object), typeof(ListBoxSelection), new PropertyMetadata(default(object)));

    public object LastSelected
    {
        get
        {
            return (object)GetValue(LastSelectedProperty);
        }
        set
        {
            SetValue(LastSelectedProperty, value);
        }
    }

    protected override void OnAttached()
    {
        base.OnAttached();

        AssociatedObject.SelectionChanged += AssociatedObject_SelectionChanged;
    }

    private void AssociatedObject_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
//you can also use whatever logic if you evaluate e.RemovedItems and e.AddedItems
        if ((AssociatedObject?.SelectedItems?.Count??0)>0)
        {
            LastSelected = AssociatedObject.SelectedItems[AssociatedObject.SelectedItems.Count-1];
        }
        else
        {
            LastSelected = null;
        }

    }

    protected override void OnDetaching()
    {
        base.OnDetaching();
        AssociatedObject.SelectionChanged -= AssociatedObject_SelectionChanged;
    }
}

XAML:

xmlns:i="clr-namespace:System.Windows.Interactivity;assembly=System.Windows.Interactivity" xmlns:b="clr-namespace:NameSpaceWhereBahaviorDefined"

<ListBox ...>
    <i:Interaction.Behaviors>
        <b:ListBoxSelection LastSelected = "{Binding VMSelection}" />
    </i:Interaction.Behaviors>
</ListBox>

WPF ListBox 多项选择不会在模型上引发 SelectedItem

WPF ListBox multiple selection not raise SelectedItem on model

c#

wpf

listbox

mvvm

inotifypropertychanged