小编Ari*_*ris的帖子

我有一个CustomControl包含ListBox:

<UserControl x:Class="WpfApplication1.CustomList"
             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" 
             mc:Ignorable="d" 
             d:DesignHeight="300" d:DesignWidth="300">
    <Grid>
        <ListBox Name="listBox1" ItemsSource="{Binding ListSource}" />
    </Grid>
</UserControl>

我ItemsSource使用Code Behind中的属性绑定:

public partial class CustomList : UserControl, INotifyPropertyChanged
    {
        public CustomList( )
        {
            InitializeComponent( );
        }

        public ObservableCollection<object> ListSource
        {
            get
            {
                return (ObservableCollection<object>)GetValue( ListSourceProperty );
            }
            set
            {
                base.SetValue(CustomList.ListSourceProperty, value);
                NotifyPropertyChanged( "ListSource" );
            }
        }

        public static DependencyProperty ListSourceProperty = DependencyProperty.Register(
             "ListSource",
             typeof( ObservableCollection<object> ),
             typeof( CustomList ),
             new PropertyMetadata( OnValueChanged ) );

        private …

我有这个Custom UserControl,它有一个List和一个Button:

<UserControl x:Class="WpfApplication1.CustomList"
         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" 
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300">
    <Grid>
        <ListBox Name="listBox1" ItemsSource="{Binding ListSource}" HorizontalAlignment="Right" Width="174" />
        <Button Name="ButtonAdd" Content="Add" HorizontalAlignment="Left" Width="101" />
    </Grid>
</UserControl>

后面的代码有一个Type IEnumerable的DependencyProperty和一个Button的处理程序(OnAdd):

public partial class CustomList : UserControl
{
    public CustomList( )
    {
        InitializeComponent( );
    ButtonAdd.Click += new RoutedEventHandler( OnAdd );
    }

private void OnAdd( object sender, EventArgs e )
{
    IList<object> tmpList = this.ListSource.ToList( );
    Article tmpArticle = new Article( );
    tmpArticle .Name = "g";
    tmpList.Add(tmpArticle );
    ListSource = (IEnumerable<object>) tmpList;
} …

如果 SomeProperty 值为 10，我想更改 ListBox 中第一项的边距，而无需代码隐藏。这是我到目前为止：

<ListBox  x:Class="Windows.CustomList"
                 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:local="clr-namespace:Windows"
                 mc:Ignorable="d" x:Name="MyList"
                 d:DesignHeight="300" d:DesignWidth="300">
    <ListBox.ItemContainerStyle>
        <Style TargetType="{x:Type ListBoxItem}">
            <Style.Triggers>
                <MultiDataTrigger>
                    <MultiDataTrigger.Conditions>
                        <Condition Binding="{Binding Path=SomeProperty}" Value="10"/>
                        <Condition Binding="{Binding Path=Items.Count, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type ListBox}}}" Value="1" />
                    </MultiDataTrigger.Conditions>
                    <Setter Property="Margin">
                        <Setter.Value>
                            <Thickness Left="500"/>
                        </Setter.Value>
                    </Setter>
                </MultiDataTrigger>
            </Style.Triggers>
        </Style>
    </ListBox.ItemContainerStyle>
    <ListBox.ItemTemplate>
        <DataTemplate>
            <local:ListBoxItemCustomTemplate/>
        </DataTemplate>
    </ListBox.ItemTemplate>
    <ListBox.ItemsPanel>
        <ItemsPanelTemplate>
            <WrapPanel Orientation="Horizontal"/>
        </ItemsPanelTemplate>
    </ListBox.ItemsPanel>
</ListBox>

当我尝试这种方法时，我得到：

System.Windows.Data 错误：4：无法找到引用“RelativeSource FindAncestor、AncestorType='ListBox'、AncestorLevel='1'”的绑定源。BindingExpression:Path=Items.Count; 数据项=空；目标元素是 'ListBox' (Name=''); 目标属性是“NoTarget”（类型“Object”）

如果我只有第一个条件，它会正确应用边距。我尝试的另一种方法是使用 ElementName：

这种方法不会出现任何错误，但也不起作用。

任何帮助将非常感激。