Pete O'Hanlon
Попробуйте изменить стиль на этот:
<Style x:Key="ScrollBarTrackThumb"
TargetType="{x:Type Thumb}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type Thumb}">
<Grid x:Name="Grid">
<Rectangle HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
Width="Auto"
Height="Auto"
Fill="Transparent" />
<Border x:Name="CornerScrollBarRectangle"
CornerRadius="8"
HorizontalAlignment="Stretch"
VerticalAlignment="Stretch"
Width="Auto"
Height="Auto"
Margin="0,1,0,1"
Background="{TemplateBinding Background}" />
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="Tag"
Value="Horizontal">
<Setter TargetName="CornerScrollBarRectangle"
Property="Width"
Value="Auto" />
<Setter TargetName="CornerScrollBarRectangle"
Property="Height"
Value="6" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<Style TargetType="{x:Type ScrollBar}">
<Setter Property="Width" Value="4" />
<Setter Property="Stylus.IsFlicksEnabled"
Value="false" />
<Setter Property="Foreground"
Value="#ADABAB" />
<Setter Property="Background"
Value="Transparent" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ScrollBar}">
<Grid x:Name="GridRoot"
Background="{TemplateBinding Background}">
<Grid.RowDefinitions>
<RowDefinition Height="0.00001*" />
</Grid.RowDefinitions>
<Track x:Name="PART_Track"
Grid.Row="0"
IsDirectionReversed="true"
Focusable="false">
<Track.Thumb>
<Thumb x:Name="Thumb"
Background="{TemplateBinding Foreground}"
Style="{DynamicResource ScrollBarTrackThumb}" />
</Track.Thumb>
<Track.IncreaseRepeatButton>
<RepeatButton x:Name="PageUp"
Command="ScrollBar.PageDownCommand"
Opacity="0"
Focusable="false" />
</Track.IncreaseRepeatButton>
<Track.DecreaseRepeatButton>
<RepeatButton x:Name="PageDown"
Command="ScrollBar.PageUpCommand"
Opacity="0"
Focusable="false" />
</Track.DecreaseRepeatButton>
</Track>
</Grid>
<ControlTemplate.Triggers>
<Trigger SourceName="Thumb"
Property="IsMouseOver"
Value="true">
<Setter Value="{DynamicResource ButtonSelectBrush}"
TargetName="Thumb"
Property="Background" />
</Trigger>
<Trigger SourceName="Thumb"
Property="IsDragging"
Value="true">
<Setter Value="{DynamicResource DarkBrush}"
TargetName="Thumb"
Property="Background" />
</Trigger>
<Trigger Property="IsEnabled"
Value="false">
<Setter TargetName="Thumb"
Property="Visibility"
Value="Collapsed" />
</Trigger>
<Trigger Property="Orientation"
Value="Horizontal">
<Setter TargetName="GridRoot"
Property="LayoutTransform">
<Setter.Value>
<RotateTransform Angle="-90" />
</Setter.Value>
</Setter>
<Setter TargetName="PART_Track"
Property="LayoutTransform">
<Setter.Value>
<RotateTransform Angle="-90" />
</Setter.Value>
</Setter>
<Setter Property="Width"
Value="Auto" />
<Setter Property="Height"
Value="6" />
<Setter TargetName="Thumb"
Property="Tag"
Value="Horizontal" />
<Setter TargetName="PageDown"
Property="Command"
Value="ScrollBar.PageLeftCommand" />
<Setter TargetName="PageUp"
Property="Command"
Value="ScrollBar.PageRightCommand" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Этого должно хватить.