Question

我的列表框有问题我已经将ListBox选择模式设置为Multiple 问题在于，Selected Item仅触发一次，而当我选择其他项时，它不会在视图模型上更改SelectedItem。我确定选择了它们，因为在选择它们时我将属性绑定到true，但是所选项目不会更新。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不会更新SelectedItem，但我可以看到选择了B 当我取消选择A时，ViewModel将SelectedItem更新为null 有人已经面临这个问题吗？我的主要目标是使SelectedItem更新为我选择的他是我的View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ViewModel：

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

我尝试过：TwoWay绑定/ UpdateTriggerSource

Answer 1

由于您选择了Multiple，因此SelectedItem将始终是您选择中的第一个选择。要获取最后选择的项目，您必须注册SelectionChanged事件并访问SelectedItems属性，该属性包含您选择的所有项目。您可以使用某种行为来实现它，因为您可以重用它。

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

1 个答案: