强制 ComboBox 在 Silverlight 中打开？

Question

我在 Silverlight 中有一个行为非常不一致的 ComboBox。

我将 ComboBox 绑定到添加或删除元素的动态数据集合。这是 ComboBox 的 XAML：

<ComboBox Margin="0,-1,0,0" Width="20" Grid.Row="0" Grid.Column="0" ItemsSource="{Binding RelativeSource={RelativeSource TemplatedParent}, Path=ItemsContained}" x:Name="TabComboBox" >
    <ComboBox.ItemsPanel>
        <ItemsPanelTemplate>
            <StackPanel Background="White" MinWidth="250" />
        </ItemsPanelTemplate>
    </ComboBox.ItemsPanel>
</ComboBox>

所以这很好用，ComboBox 会“打开”ItemsContained 中的一长串项目。但是，如果我删除 ItemsContained 中的一个项目，当你单击它时，组合框会突然从打开“向上”切换到打开“向下”，尽管事实上这个集合中有很多项目并且那里只有 20 像素左右的空间供它向下打开。我无法弄清楚这一点。我什至尝试将 ItemsPanelTemplate 设置为 MinHeight，但这无济于事。有谁知道如何让 ComboBox 总是“打开”？

此外，即使我将 MinHeight 设置为荒谬的值，例如 10,000，它仍然会这样做。

编辑：作为更新，我通过在每次更改 ItemsContained 时创建一个全新的 ComboBox 来实现此功能。这是代码：

scrollingGrid.Children.Remove(tabComboBox);
tabComboBox.ItemsSource = null;
ComboBox boxy = new ComboBox()
{
    ItemsSource = ItemsContained
};
scrollingGrid.Children.Add(boxy);
tabComboBox = boxy;

我觉得这有点临时，所以如果有人有更好的想法，请告诉我。更改 ComboBox 内 ScrollViewer 的高度也不起作用。

Answer 1

我认为这是一个 Silverlight 错误。当您设置 ItemsSource 属性时，组合框弹出窗口的行为会从上变为下。

我在每个组合框的 DropDownClosed 事件中克隆我的组合框，这对我有用。

 Private Sub cbRow1_DropDownClosed(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cbRow1.DropDownClosed, cbRow2.DropDownClosed, cbRow3.DropDownClosed, cbRow4.DropDownClosed, cbRow5.DropDownClosed
    Dim co As ComboBox = CType(sender, ComboBox)
    CloneComboBox(co)
End Sub

Private Sub CloneComboBox(ByVal co As ComboBox)
    Dim cbClon = New ComboBox()
    cbClon.Margin = co.Margin
    cbClon.Width = co.Width
    cbClon.Height = co.Height
    cbClon.Name = co.Name
    cbClon.Tag = co.Tag

    cbClon.ItemsSource = co.ItemsSource
    cbClon.SelectedIndex = co.SelectedIndex

    LayoutRoot.Children.Remove(co)
    LayoutRoot.Children.Add(cbClon)

    //this is because I have my comboboxes inside a grid
    System.Windows.Controls.Grid.SetRow(cbClon, cbClon.Tag)
    System.Windows.Controls.Grid.SetColumn(cbClon, 0)


    AddHandler cbClon.DropDownClosed, AddressOf cbRow1_DropDownClosed

End Sub

Answer 2

我不确定此解决方案是否会比您当前的解决方案更临时，但我想我会提供它。

我编辑了 ComboBox 模板的一个副本，在原来的 ItemsPresenter 中只有一个 ScrollViewer 的地方，我添加了一个边距为 0,5000,0,0 的 Rectangle，以便内部弹出代码将其放在顶部总是。我还将模板绑定移​​动到 ScrollViewer，这样即使没有足够的项目，它也不会伸展到顶部。

样式有点长，但在这里，只需将其放入资源 xaml 中（并将 ComboBox 的样式设置为 ComboBoxStyle1）。告诉我它是如何为您工作的！

<ControlTemplate x:Key="ValidationToolTipTemplate">
        <Grid x:Name="Root" Margin="5,0" Opacity="0" RenderTransformOrigin="0,0">
            <Grid.RenderTransform>
                <TranslateTransform x:Name="xform" X="-25"/>
            </Grid.RenderTransform>
            <VisualStateManager.VisualStateGroups>
                <VisualStateGroup x:Name="OpenStates">
                    <VisualStateGroup.Transitions>
                        <VisualTransition GeneratedDuration="0"/>
                        <VisualTransition GeneratedDuration="0:0:0.2" To="Open">
                            <Storyboard>
                                <DoubleAnimation Duration="0:0:0.2" To="0" Storyboard.TargetProperty="X" Storyboard.TargetName="xform">
                                    <DoubleAnimation.EasingFunction>
                                        <BackEase Amplitude=".3" EasingMode="EaseOut"/>
                                    </DoubleAnimation.EasingFunction>
                                </DoubleAnimation>
                                <DoubleAnimation Duration="0:0:0.2" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Root"/>
                            </Storyboard>
                        </VisualTransition>
                    </VisualStateGroup.Transitions>
                    <VisualState x:Name="Closed">
                        <Storyboard>
                            <DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Root"/>
                        </Storyboard>
                    </VisualState>
                    <VisualState x:Name="Open">
                        <Storyboard>
                            <DoubleAnimation Duration="0" To="0" Storyboard.TargetProperty="X" Storyboard.TargetName="xform"/>
                            <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Root"/>
                        </Storyboard>
                    </VisualState>
                </VisualStateGroup>
            </VisualStateManager.VisualStateGroups>
            <Border Background="#052A2E31" CornerRadius="5" Margin="4,4,-4,-4"/>
            <Border Background="#152A2E31" CornerRadius="4" Margin="3,3,-3,-3"/>
            <Border Background="#252A2E31" CornerRadius="3" Margin="2,2,-2,-2"/>
            <Border Background="#352A2E31" CornerRadius="2" Margin="1,1,-1,-1"/>
            <Border Background="#FFDC000C" CornerRadius="2"/>
            <Border CornerRadius="2">
                <TextBlock Foreground="White" MaxWidth="250" Margin="8,4,8,4" TextWrapping="Wrap" Text="{Binding (Validation.Errors)[0].ErrorContent}" UseLayoutRounding="false"/>
            </Border>
        </Grid>
    </ControlTemplate>
    <Style x:Key="ComboBoxStyle1" TargetType="ComboBox">
        <Setter Property="Padding" Value="6,2,25,2"/>
        <Setter Property="Background" Value="#FF1F3B53"/>
        <Setter Property="HorizontalContentAlignment" Value="Left"/>
        <Setter Property="BorderThickness" Value="1"/>
        <Setter Property="TabNavigation" Value="Once"/>
        <Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Auto"/>
        <Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto"/>
        <Setter Property="BorderBrush">
            <Setter.Value>
                <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                    <GradientStop Color="#FFA3AEB9" Offset="0"/>
                    <GradientStop Color="#FF8399A9" Offset="0.375"/>
                    <GradientStop Color="#FF718597" Offset="0.375"/>
                    <GradientStop Color="#FF617584" Offset="1"/>
                </LinearGradientBrush>
            </Setter.Value>
        </Setter>
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="ComboBox">
                    <Grid>
                        <Grid.Resources>
                            <Style x:Name="comboToggleStyle" TargetType="ToggleButton">
                                <Setter Property="Foreground" Value="#FF333333"/>
                                <Setter Property="Background" Value="#FF1F3B53"/>
                                <Setter Property="BorderBrush">
                                    <Setter.Value>
                                        <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                                            <GradientStop Color="#FFA3AEB9" Offset="0"/>
                                            <GradientStop Color="#FF8399A9" Offset="0.375"/>
                                            <GradientStop Color="#FF718597" Offset="0.375"/>
                                            <GradientStop Color="#FF617584" Offset="1"/>
                                        </LinearGradientBrush>
                                    </Setter.Value>
                                </Setter>
                                <Setter Property="BorderThickness" Value="1"/>
                                <Setter Property="Padding" Value="3"/>
                                <Setter Property="Template">
                                    <Setter.Value>
                                        <ControlTemplate TargetType="ToggleButton">
                                            <Grid>
                                                <VisualStateManager.VisualStateGroups>
                                                    <VisualStateGroup x:Name="CommonStates">
                                                        <VisualState x:Name="Normal"/>
                                                        <VisualState x:Name="MouseOver">
                                                            <Storyboard>
                                                                <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="BackgroundOverlay"/>
                                                                <ColorAnimation Duration="0" To="#7FFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[3].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
                                                                <ColorAnimation Duration="0" To="#CCFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[2].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
                                                                <ColorAnimation Duration="0" To="#F2FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
                                                            </Storyboard>
                                                        </VisualState>
                                                        <VisualState x:Name="Pressed">
                                                            <Storyboard>
                                                                <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="BackgroundOverlay2"/>
                                                                <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Highlight"/>
                                                                <ColorAnimation Duration="0" To="#E5FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
                                                                <ColorAnimation Duration="0" To="#BCFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[2].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
                                                                <ColorAnimation Duration="0" To="#6BFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[3].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
                                                                <ColorAnimation Duration="0" To="#F2FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient"/>
                                                            </Storyboard>
                                                        </VisualState>
                                                        <VisualState x:Name="Disabled"/>
                                                    </VisualStateGroup>
                                                    <VisualStateGroup x:Name="CheckStates">
                                                        <VisualState x:Name="Checked">
                                                            <Storyboard>
                                                                <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="BackgroundOverlay3"/>
                                                                <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="Highlight"/>
                                                                <DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="BackgroundGradient2"/>
                                                                <ColorAnimation Duration="0" To="#E5FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[1].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient2"/>
                                                                <ColorAnimation Duration="0" To="#BCFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[2].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient2"/>
                                                                <ColorAnimation Duration="0" To="#6BFFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[3].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient2"/>
                                                                <ColorAnimation Duration="0" To="#F2FFFFFF" Storyboard.TargetProperty="(Shape.Fill).(GradientBrush.GradientStops)[0].(GradientStop.Color)" Storyboard.TargetName="BackgroundGradient2"/>
                                                            </Storyboard>
                                                        </VisualState>
                                                        <VisualState x:Name="Unchecked"/>
                                                    </VisualStateGroup>
                                                    <VisualStateGroup x:Name="FocusStates">
                                                        <VisualState x:Name="Focused">
                                                            <Storyboard>
                                                                <ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="FocusVisualElement">
                                                                    <DiscreteObjectKeyFrame KeyTime="0">
                                                                        <DiscreteObjectKeyFrame.Value>
                                                                            <Visibility>Visible</Visibility>
                                                                        </DiscreteObjectKeyFrame.Value>
                                                                    </DiscreteObjectKeyFrame>
                                                                </ObjectAnimationUsingKeyFrames>
                                                            </Storyboard>
                                                        </VisualState>
                                                        <VisualState x:Name="Unfocused"/>
                                                    </VisualStateGroup>
                                                </VisualStateManager.VisualStateGroups>
                                                <Rectangle x:Name="Background" Fill="{TemplateBinding Background}" RadiusY="3" RadiusX="3" Stroke="{TemplateBinding BorderBrush}" StrokeThickness="{TemplateBinding BorderThickness}"/>
                                                <Rectangle x:Name="BackgroundOverlay" Fill="#FF448DCA" Opacity="0" RadiusY="3" RadiusX="3" Stroke="#00000000" StrokeThickness="{TemplateBinding BorderThickness}"/>
                                                <Rectangle x:Name="BackgroundOverlay2" Fill="#FF448DCA" Opacity="0" RadiusY="3" RadiusX="3" Stroke="#00000000" StrokeThickness="{TemplateBinding BorderThickness}"/>
                                                <Rectangle x:Name="BackgroundGradient" Margin="{TemplateBinding BorderThickness}" RadiusY="2" RadiusX="2" Stroke="#FFFFFFFF" StrokeThickness="1">
                                                    <Rectangle.Fill>
                                                        <LinearGradientBrush EndPoint=".7,1" StartPoint=".7,0">
                                                            <GradientStop Color="#FFFFFFFF" Offset="0"/>
                                                            <GradientStop Color="#F9FFFFFF" Offset="0.375"/>
                                                            <GradientStop Color="#E5FFFFFF" Offset="0.625"/>
                                                            <GradientStop Color="#C6FFFFFF" Offset="1"/>
                                                        </LinearGradientBrush>
                                                    </Rectangle.Fill>
                                                </Rectangle>
                                                <Rectangle x:Name="BackgroundOverlay3" Fill="#FF448DCA" Opacity="0" RadiusY="3" RadiusX="3" Stroke="#00000000" StrokeThickness="{TemplateBinding BorderThickness}"/>
                                                <Rectangle x:Name="BackgroundGradient2" Margin="{TemplateBinding BorderThickness}" Opacity="0" RadiusY="2" RadiusX="2" Stroke="#FFFFFFFF" StrokeThickness="1">
                                                    <Rectangle.Fill>
                                                        <LinearGradientBrush EndPoint=".7,1" StartPoint=".7,0">
                                                            <GradientStop Color="#FFFFFFFF" Offset="0"/>
                                                            <GradientStop Color="#F9FFFFFF" Offset="0.375"/>
                                                            <GradientStop Color="#E5FFFFFF" Offset="0.625"/>
                                                            <GradientStop Color="#C6FFFFFF" Offset="1"/>
                                                        </LinearGradientBrush>
                                                    </Rectangle.Fill>
                                                </Rectangle>
                                                <Rectangle x:Name="Highlight" IsHitTestVisible="false" Margin="{TemplateBinding BorderThickness}" Opacity="0" RadiusY="2" RadiusX="2" Stroke="#FF6DBDD1" StrokeThickness="1"/>
                                                <ContentPresenter x:Name="contentPresenter" ContentTemplate="{TemplateBinding ContentTemplate}" Content="{TemplateBinding Content}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/>
                                                <Rectangle x:Name="FocusVisualElement" IsHitTestVisible="false" Margin="1" RadiusY="3.5" RadiusX="3.5" Stroke="#FF6DBDD1" StrokeThickness="1" Visibility="Collapsed"/>
                                            </Grid>
                                        </ControlTemplate>
                                    </Setter.Value>
                                </Setter>
                            </Style>
                        </Grid.Resources>
                        <VisualStateManager.VisualStateGroups>
                            <VisualStateGroup x:Name="CommonStates">
                                <VisualState x:Name="Normal"/>
                                <VisualState x:Name="MouseOver"/>
                                <VisualState x:Name="Disabled">
                                    <Storyboard>
                                        <DoubleAnimation Duration="00:00:00" To=".55" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="DisabledVisualElement"/>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                            <VisualStateGroup x:Name="FocusStates">
                                <VisualState x:Name="Focused">
                                    <Storyboard>
                                        <DoubleAnimation Duration="00:00:00" To="1" Storyboard.TargetProperty="(UIElement.Opacity)" Storyboard.TargetName="FocusVisualElement"/>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="Unfocused"/>
                                <VisualState x:Name="FocusedDropDown">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Duration="00:00:00" Storyboard.TargetProperty="(UIElement.Visibility)" Storyboard.TargetName="PopupBorder">
                                            <DiscreteObjectKeyFrame KeyTime="00:00:00">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <Visibility>Visible</Visibility>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                            <VisualStateGroup x:Name="ValidationStates">
                                <VisualState x:Name="Valid"/>
                                <VisualState x:Name="InvalidUnfocused">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="ValidationErrorElement">
                                            <DiscreteObjectKeyFrame KeyTime="0">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <Visibility>Visible</Visibility>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                                <VisualState x:Name="InvalidFocused">
                                    <Storyboard>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Visibility" Storyboard.TargetName="ValidationErrorElement">
                                            <DiscreteObjectKeyFrame KeyTime="0">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <Visibility>Visible</Visibility>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                        <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="IsOpen" Storyboard.TargetName="validationTooltip">
                                            <DiscreteObjectKeyFrame KeyTime="0">
                                                <DiscreteObjectKeyFrame.Value>
                                                    <System:Boolean>True</System:Boolean>
                                                </DiscreteObjectKeyFrame.Value>
                                            </DiscreteObjectKeyFrame>
                                        </ObjectAnimationUsingKeyFrames>
                                    </Storyboard>
                                </VisualState>
                            </VisualStateGroup>
                        </VisualStateManager.VisualStateGroups>
                        <Border x:Name="ContentPresenterBorder">
                            <Grid>
                                <ToggleButton x:Name="DropDownToggle" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" HorizontalAlignment="Stretch" HorizontalContentAlignment="Right" Margin="0" Style="{StaticResource comboToggleStyle}" VerticalAlignment="Stretch">
                                    <Path x:Name="BtnArrow" Data="F1 M 301.14,-189.041L 311.57,-189.041L 306.355,-182.942L 301.14,-189.041 Z " HorizontalAlignment="Right" Height="4" Margin="0,0,6,0" Stretch="Uniform" Width="8">
                                        <Path.Fill>
                                            <SolidColorBrush x:Name="BtnArrowColor" Color="#FF333333"/>
                                        </Path.Fill>
                                    </Path>
                                </ToggleButton>
                                <ContentPresenter x:Name="ContentPresenter" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}">
                                    <TextBlock Text=" "/>
                                </ContentPresenter>
                            </Grid>
                        </Border>
                        <Rectangle x:Name="DisabledVisualElement" Fill="White" IsHitTestVisible="false" Opacity="0" RadiusY="3" RadiusX="3"/>
                        <Rectangle x:Name="FocusVisualElement" IsHitTestVisible="false" Margin="1" Opacity="0" RadiusY="2" RadiusX="2" Stroke="#FF6DBDD1" StrokeThickness="1"/>
                        <Border x:Name="ValidationErrorElement" BorderBrush="#FFDB000C" BorderThickness="1" CornerRadius="1" Visibility="Collapsed">
                            <ToolTipService.ToolTip>
                                <ToolTip x:Name="validationTooltip" DataContext="{Binding RelativeSource={RelativeSource TemplatedParent}}" Placement="Right" PlacementTarget="{Binding RelativeSource={RelativeSource TemplatedParent}}" Template="{StaticResource ValidationToolTipTemplate}">
                                    <ToolTip.Triggers>
                                        <EventTrigger RoutedEvent="Canvas.Loaded">
                                            <BeginStoryboard>
                                                <Storyboard>
                                                    <ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="IsHitTestVisible" Storyboard.TargetName="validationTooltip">
                                                        <DiscreteObjectKeyFrame KeyTime="0">
                                                            <DiscreteObjectKeyFrame.Value>
                                                                <System:Boolean>true</System:Boolean>
                                                            </DiscreteObjectKeyFrame.Value>
                                                        </DiscreteObjectKeyFrame>
                                                    </ObjectAnimationUsingKeyFrames>
                                                </Storyboard>
                                            </BeginStoryboard>
                                        </EventTrigger>
                                    </ToolTip.Triggers>
                                </ToolTip>
                            </ToolTipService.ToolTip>
                            <Grid Background="Transparent" HorizontalAlignment="Right" Height="12" Margin="1,-4,-4,0" VerticalAlignment="Top" Width="12">
                                <Path Data="M 1,0 L6,0 A 2,2 90 0 1 8,2 L8,7 z" Fill="#FFDC000C" Margin="1,3,0,0"/>
                                <Path Data="M 0,0 L2,0 L 8,6 L8,8" Fill="#ffffff" Margin="1,3,0,0"/>
                            </Grid>
                        </Border>
                        <Popup x:Name="Popup" >
                            <Border x:Name="PopupBorder"  HorizontalAlignment="Stretch">
                                <Grid>

                                    <ScrollViewer BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}"  VerticalAlignment="Bottom" x:Name="ScrollViewer"  Padding="1">
                                        <ScrollViewer.Background>
                                            <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
                                                <GradientStop Color="White" Offset="0"/>
                                                <GradientStop Color="#FFFEFEFE" Offset="1"/>
                                            </LinearGradientBrush>
                                        </ScrollViewer.Background>
                                        <ItemsPresenter/>
                                    </ScrollViewer>
                                    <Rectangle Margin="0,5000,0,0"/>
                                </Grid>

                            </Border>
                        </Popup>
                    </Grid>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>