Creating a NumericUpDown control from scratch

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                    xmlns:local="clr-namespace:CustomControls">
    <Style TargetType="{x:Type local:NumericUpDown}">
        <Setter Property="HorizontalAlignment" Value="Center" />
        <Setter Property="HorizontalContentAlignment" Value="Right" />
        <Setter Property="VerticalAlignment" Value="Center" />
        <Setter Property="BorderBrush" Value="Gray" />
        <Setter Property="BorderThickness" Value="1" />
        <Setter Property="Width" Value="150" />
        <Setter Property="Height" Value="26" />
        <Setter Property="Focusable" Value="False" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type local:NumericUpDown}">
                    <Border Background="{TemplateBinding Background}"
                            BorderBrush="{TemplateBinding BorderBrush}"
                            BorderThickness="{TemplateBinding BorderThickness}"
                            Focusable="False">
                        <Grid Width="{TemplateBinding Width}"
                              Height="{TemplateBinding Height}"
                              VerticalAlignment="Center"
                              Focusable="False">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition Width="*" />
                                <ColumnDefinition Width="Auto" />
                            </Grid.ColumnDefinitions>

                            <TextBox x:Name="PART_TextBox"
                                     VerticalAlignment="Center"
                                     HorizontalContentAlignment="Right" />

                            <Grid Grid.Column="1">
                                <Grid.RowDefinitions>
                                    <RowDefinition Height="*" />
                                    <RowDefinition Height="*" />
                                </Grid.RowDefinitions>
                                <RepeatButton x:Name="PART_IncreaseButton"
                                              Grid.Row="0"
                                              Width="20"
                                              Margin="0, 1, 2, 0">
                                    <Path Margin="1"
                                          Data="M 0 20 L 35 -20 L 70 20 Z"
                                          Fill="#FF202020"
                                          Stretch="Uniform" />
                                </RepeatButton>
                                <RepeatButton x:Name="PART_DecreaseButton"
                                              Grid.Row="1"
                                              Width="20"
                                              Margin="0, 0, 2, 1">
                                    <Path Margin="1"
                                          Data="M 0 0 L 35 40 L 70 0 Z"
                                          Fill="#FF202020"
                                          Stretch="Uniform" />
                                </RepeatButton>
                            </Grid>
                        </Grid>
                    </Border>
                </ControlTemplate>
            </Setter.Value>
        </Setter>
    </Style>
</ResourceDictionary>