Show ScrollViewer for the Time Display Items of RadDateTimePicker

Environment

Product Version	2019.1.116
Product	RadDateTimePicker for WPF

Description

How to show a vertical scrollbar in the time section of the drop down.

Solution

1. Extract the ControlTemplate of RadClock.
2. Wrap the ItemsPresenter control of the template in a ScrollViewer control.
   
3. Create a Style targeting RadClock and define a Setter that sets the Template property to the customized ControlTemplate.
4. Apply the Style via the ClockStyle property of RadDateTimePicker.

<Window.Resources> 
    <ControlTemplate TargetType="{x:Type telerik:RadClock}" x:Key="CustomClockTemplate">       
        <Grid> 
            <Grid.RowDefinitions> 
                <RowDefinition Height="Auto"/> 
                <RowDefinition Height="*"/> 
            </Grid.RowDefinitions> 
            <Border x:Name="BackgroundVisual" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" 
                    Background="{TemplateBinding Background}" CornerRadius="0" Grid.RowSpan="2"> 
                <Border BorderBrush="White" BorderThickness="{TemplateBinding BorderThickness}" CornerRadius="0"/> 
            </Border> 
            <Border x:Name="Header" BorderBrush="Black" BorderThickness="1" CornerRadius="0" MinHeight="32"> 
                <Border.Background> 
                    <LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0"> 
                        <GradientStop Color="#FF5B5B5B" Offset="1"/> 
                        <GradientStop Color="#FF868686"/> 
                        <GradientStop Color="#FF4F4F4F" Offset="0.42"/> 
                        <GradientStop Color="#FF0E0E0E" Offset="0.43"/> 
                    </LinearGradientBrush> 
                </Border.Background> 
                <Border BorderBrush="#FFB5B5B5" BorderThickness="1" CornerRadius="0" Padding="{TemplateBinding Padding}"> 
                    <ContentControl ContentTemplate="{TemplateBinding HeaderTemplate}" Content="{TemplateBinding Header}"  
                                    Foreground="White" FontWeight="Bold" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" IsTabStop="False" Margin="{TemplateBinding Padding}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"/> 
                </Border> 
            </Border> 
            <!-- THE NEWLY ADDED SCROLLVIEWER --> 
            <ScrollViewer Grid.Row="1"> 
                <ItemsPresenter Margin="1,0,1,1" /> 
            </ScrollViewer> 
        </Grid> 
    </ControlTemplate> 
</Window.Resources> 
<Grid> 
    <telerik:RadDateTimePicker> 
        <telerik:RadDateTimePicker.ClockStyle> 
            <Style TargetType="telerik:RadClock"> 
                <Setter Property="Template" Value="{StaticResource CustomClockTemplate}" /> 
            </Style> 
        </telerik:RadDateTimePicker.ClockStyle> 
    </telerik:RadDateTimePicker> 
</Grid>     

This template is extracted from the OfficeBlack theme.