Force ComboBox to open up in Silverlight?
I have a ComboBox in Silverlight that has very inconsistent behavior.
I have the ComboBox bound to a dynamic collection of data where elements are added or removed. Here is the XAML for the ComboBox:
<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>
So this works great and the ComboBox opens "up" with the long list of items in ItemsContained. However, if I delete one of the items in ItemsContained, the ComboBox all of a sudden will switch from opening "up" to opening "down" when you click on it, despite the fact there are a lot of items in this collection and there is only 20 or so pixels of room for it to open down. I cannot figure this out. I have even tried setting the ItemsPanelTemplate to have a MinHeight, but that does not help. Does anyone know how to make the ComboBox always open "up"?
Also, even if I set the MinHeight to something ridiculous, such as 10,000, it still does this.
EDIT: As an update, I have gotten this to work by creating a whole new ComboBox every time ItemsContained is changed. This is the code:
scrollingGrid.Children.Remove(tabComboBox);
tabComboBox.ItemsSource = null;
ComboBox boxy = new ComboBox()
{
ItemsSource = ItemsContained
};
scrollingGrid.Children.Add(boxy);
tabComboBox = boxy;
I feel this is a little ad hoc, so if anyone has a better idea, let me know. Changing the height of the ScrollViewer inside the ComboBox does not work either.
I think this is a Silverlight Bug. When you set the ItemsSource property the behavior of the combobox popup changes from up to down.
I Clone my combobox in the event DropDownClosed of each combobox and that works for me.
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
I'm not sure this solution will be any less ad hoc than your current fix, but I figured I'd offer it.
I edited a copy of the ComboBox template, and where the original only had a ScrollViewer in an ItemsPresenter, I added a Rectangle with Margin 0,5000,0,0, so that the internal Popup code would place it on the top always. I also moved the template bindings to the ScrollViewer so that it wouldn't stretch to the top even if there weren't enough items.
The style is a little long but here it is, just throw it in your resources xaml (and set the style of your ComboBox to ComboBoxStyle1). Let me know how it works for you!
<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>
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