コンボボックスのドロップダウン リストを、コンボボックスの contentPresenter のオフセット (選択した項目を表示する部分) から直接開く必要があります。しかし実際には、ドロップダウン リストのオフセットが contentPresenter の上にあり、ページの上限まであるということが起こります。
同様に、ドロップダウンリストの幅を最大のアイテムに合わせて永続的に変更し、現在のように動的に変更しないようにします(現在、表示されているアイテムに応じてサイズが変更されました)。
コンボ ボックスの MaxDropDownHeight プロパティを 0 または 300 に設定しようとしましたが、何も変わりません。
これが templateControl です (画像はこのスニペットとは関係ありません):
<Style TargetType="ComboBox" >
<Setter Property="Padding" Value="8,0" />
<Setter Property="FlowDirection" Value="LeftToRight" />
<Setter Property="Foreground" Value="{StaticResource ComboBoxForegroundThemeBrush}" />
<Setter Property="Background" Value="White" />
<Setter Property="BorderBrush" Value="Gray" />
<Setter Property="BorderThickness" Value="1" />
<Setter Property="TabNavigation" Value="Once" />
<Setter Property="ScrollViewer.HorizontalScrollBarVisibility" Value="Disabled" />
<Setter Property="ScrollViewer.VerticalScrollBarVisibility" Value="Auto" />
<Setter Property="ScrollViewer.HorizontalScrollMode" Value="Disabled" />
<Setter Property="ScrollViewer.VerticalScrollMode" Value="Auto" />
<Setter Property="ScrollViewer.IsVerticalRailEnabled" Value="True" />
<Setter Property="ScrollViewer.IsDeferredScrollingEnabled" Value="False" />
<Setter Property="ScrollViewer.BringIntoViewOnFocusChange" Value="True" />
<Setter Property="HorizontalContentAlignment" Value="Stretch" />
<Setter Property="FontFamily" Value="{StaticResource ContentControlThemeFontFamily}" />
<Setter Property="FontSize" Value="{StaticResource ControlContentThemeFontSize}" />
<Setter Property="ItemsPanel">
<Setter.Value>
<ItemsPanelTemplate>
<CarouselPanel />
</ItemsPanelTemplate>
</Setter.Value>
</Setter>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ComboBox">
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*" />
<ColumnDefinition Width="32" />
</Grid.ColumnDefinitions>
<VisualStateManager.VisualStateGroups>
<VisualStateGroup x:Name="CommonStates">
<VisualState x:Name="Normal" />
<VisualState x:Name="PointerOver">
<!--
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="Background">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxPointerOverBackgroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="Background">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxPointerOverBorderThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Fill" Storyboard.TargetName="Highlight">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxSelectedPointerOverBackgroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
-->
</VisualState>
<VisualState x:Name="Pressed">
<!--
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="Background">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxPressedBackgroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="Background">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxPressedBorderThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentPresenter">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxPressedForegroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="PressedBackground"/>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="DropDownGlyph">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxArrowPressedForegroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
-->
</VisualState>
<VisualState x:Name="Disabled">
<!--
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Background" Storyboard.TargetName="Background">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxDisabledBackgroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="BorderBrush" Storyboard.TargetName="Background">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxDisabledBorderThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentPresenter">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxDisabledForegroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="DropDownGlyph">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxArrowDisabledForegroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
-->
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="FocusStates">
<VisualState x:Name="Focused">
<!--
<Storyboard>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="HighlightBackground"/>
<DoubleAnimation Duration="0" To="1" Storyboard.TargetProperty="Opacity" Storyboard.TargetName="Highlight"/>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentPresenter">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxFocusedForegroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
-->
</VisualState>
<VisualState x:Name="FocusedPressed">
<!--
<Storyboard>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Foreground" Storyboard.TargetName="ContentPresenter">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxPressedForegroundThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
<ObjectAnimationUsingKeyFrames Storyboard.TargetProperty="Fill" Storyboard.TargetName="Highlight">
<DiscreteObjectKeyFrame KeyTime="0" Value="{StaticResource ComboBoxPressedHighlightThemeBrush}"/>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
-->
</VisualState>
<VisualState x:Name="Unfocused" />
<VisualState x:Name="PointerFocused" />
<VisualState x:Name="FocusedDropDown">
<!--
<Storyboard>
<ObjectAnimationUsingKeyFrames Duration="0" Storyboard.TargetProperty="Visibility" Storyboard.TargetName="PopupBorder">
<DiscreteObjectKeyFrame KeyTime="0">
<DiscreteObjectKeyFrame.Value>
<Visibility>Visible</Visibility>
</DiscreteObjectKeyFrame.Value>
</DiscreteObjectKeyFrame>
</ObjectAnimationUsingKeyFrames>
</Storyboard>
-->
</VisualState>
</VisualStateGroup>
<VisualStateGroup x:Name="DropDownStates">
<VisualState x:Name="Opened">
<!--
<Storyboard>
<SplitOpenThemeAnimation ClosedTargetName="ContentPresenter" ContentTranslationOffset="0" ContentTargetName="ScrollViewer" ClosedLength="{Binding TemplateSettings.DropDownClosedHeight, RelativeSource={RelativeSource Mode=TemplatedParent}}" OffsetFromCenter="{Binding TemplateSettings.DropDownOffset, RelativeSource={RelativeSource Mode=TemplatedParent}}" OpenedTargetName="PopupBorder" OpenedLength="{Binding TemplateSettings.DropDownOpenedHeight, RelativeSource={RelativeSource Mode=TemplatedParent}}"/>
</Storyboard>
-->
</VisualState>
<VisualState x:Name="Closed">
<!--
<Storyboard>
<SplitCloseThemeAnimation ClosedTargetName="ContentPresenter" ContentTranslationOffset="40" ContentTranslationDirection="{Binding TemplateSettings.SelectedItemDirection, RelativeSource={RelativeSource Mode=TemplatedParent}}" ContentTargetName="ScrollViewer" ClosedLength="{Binding TemplateSettings.DropDownClosedHeight, RelativeSource={RelativeSource Mode=TemplatedParent}}" OffsetFromCenter="{Binding TemplateSettings.DropDownOffset, RelativeSource={RelativeSource Mode=TemplatedParent}}" OpenedTargetName="PopupBorder" OpenedLength="{Binding TemplateSettings.DropDownOpenedHeight, RelativeSource={RelativeSource Mode=TemplatedParent}}"/>
</Storyboard>
-->
</VisualState>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
<Border x:Name="Background"
Grid.ColumnSpan="2"
Background="{TemplateBinding Background}"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
CornerRadius="2" />
<Rectangle x:Name="PressedBackground"
Margin="{TemplateBinding BorderThickness}"
Fill="{StaticResource ComboBoxPressedHighlightThemeBrush}"
Opacity="0" />
<Border x:Name="HighlightBackground"
Grid.ColumnSpan="2"
Background="{StaticResource ComboBoxFocusedBackgroundThemeBrush}"
BorderBrush="{StaticResource ComboBoxFocusedBorderThemeBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
Opacity="0" />
<Rectangle x:Name="Highlight"
Margin="{TemplateBinding BorderThickness}"
Fill="{StaticResource ComboBoxSelectedBackgroundThemeBrush}"
Opacity="0" />
<ContentPresenter x:Name="ContentPresenter"
Margin="{TemplateBinding Padding}"
HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}" />
<TextBlock x:Name="DropDownGlyph"
Grid.Column="1"
Margin="0,0,6,4"
HorizontalAlignment="Right"
VerticalAlignment="Center"
FontFamily="{StaticResource SymbolThemeFontFamily}"
FontSize="{StaticResource ComboBoxArrowThemeFontSize}"
FontWeight="Bold"
Foreground="Red"
IsHitTestVisible="False"
Text="" />
<Popup x:Name="Popup">
<Border x:Name="PopupBorder"
HorizontalAlignment="Stretch"
Background="{StaticResource ComboBoxPopupBackgroundThemeBrush}"
BorderBrush="{StaticResource ComboBoxPopupBorderThemeBrush}"
BorderThickness="{StaticResource ComboBoxPopupBorderThemeThickness}">
<ScrollViewer x:Name="ScrollViewer"
BringIntoViewOnFocusChange="{TemplateBinding ScrollViewer.BringIntoViewOnFocusChange}"
Foreground="{StaticResource ComboBoxPopupForegroundThemeBrush}"
HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
HorizontalScrollMode="{TemplateBinding ScrollViewer.HorizontalScrollMode}"
IsDeferredScrollingEnabled="{TemplateBinding ScrollViewer.IsDeferredScrollingEnabled}"
IsHorizontalRailEnabled="{TemplateBinding ScrollViewer.IsHorizontalRailEnabled}"
IsVerticalRailEnabled="{TemplateBinding ScrollViewer.IsVerticalRailEnabled}"
VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}"
VerticalScrollMode="{TemplateBinding ScrollViewer.VerticalScrollMode}"
VerticalSnapPointsAlignment="Near"
VerticalSnapPointsType="OptionalSingle"
ZoomMode="Disabled">
<ItemsPresenter />
</ScrollViewer>
</Border>
</Popup>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
ありがとう!