[Solved] Why there is a gap?

[Pavel]

Trying to align control and fond that there is a gap like top margin and I can't remove it. Screenshot attached.
Left control is DateTimePicker - right control is textbox.

[Pavel]

Same thing with RadNumericBox.

[Pavel]

Found it. It's HeaderStyle and it doesn't looks good. Because picker have no header, but there is margin.

<Setter Property="HeaderStyle">
           <Setter.Value>
               <Style TargetType="ContentControl">
                   <Setter Property="HorizontalAlignment" Value="Stretch"/>
                   <Setter Property="VerticalAlignment" Value="Stretch"/>
                   <Setter Property="HorizontalContentAlignment" Value="Stretch"/>
                   <Setter Property="VerticalContentAlignment" Value="Stretch"/>
                   <Setter Property="Margin" Value="0 0 0 4"/>
                   <Setter Property="FontSize" Value="{StaticResource ControlContentThemeFontSize}"/>
                   <Setter Property="Foreground" Value="{ThemeResource TelerikDateTimePickerHeaderForegroundBrush}"/>
               </Style>
           </Setter.Value>
       </Setter>