<Style x:Key="DataPointStyle1" TargetType="toolkit:ColumnDataPoint">
<Setter Property="Width" Value="10"/>
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="toolkit:ColumnDataPoint">
<Grid>
<Rectangle
Fill="{TemplateBinding Background}"
Stroke="Black"/>
<Grid Background="Transparent" Margin="0" HorizontalAlignment="Center" VerticalAlignment="Top">
<TextBlock Text="{TemplateBinding FormattedDependentValue}" FontWeight="Bold" Margin="0,-20,0,0" VerticalAlignment="Bottom" HorizontalAlignment="Center" />
</Grid>
<TextBlock Text="{TemplateBinding FormattedIndependentValue}" FontWeight="Bold" Margin="0,-20,0,0" VerticalAlignment="Bottom" HorizontalAlignment="Center" />
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
In Code Behind:
line.DataPointStyle = (Style)Resources["DataPointStyle1"];