IntegerTextBox.xaml

<UserControl x:Class="GraphicalMirai.IntegerTextBox"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
      xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes"
             xmlns:local="clr-namespace:GraphicalMirai"
             mc:Ignorable="d" Height="34"
             d:DesignHeight="34" d:DesignWidth="100">
    <Grid>
        <TextBox x:Name="InputBox" Text="0" LostFocus="InputBox_LostFocus" PreviewTextInput="InputBox_PreviewTextInput" TextChanged="InputBox_TextChanged" Margin="0,0,22,0" Background="#FFF" Style="{StaticResource MaterialDesignOutlinedTextBox}" Padding="10,5,10,7" FontSize="16"/>
        <Border x:Name="Buttons" Width="20" HorizontalAlignment="Right" CornerRadius="4" BorderThickness="1" BorderBrush="#000" ClipToBounds="True">
            <Grid>
                <Grid.OpacityMask>
                    <VisualBrush Visual="{Binding ElementName=mask}"/>
                </Grid.OpacityMask>
                <Grid.Resources>
                    <Style TargetType="Button" BasedOn="{StaticResource MaterialDesignFloatingActionMiniButton}">
                        <Setter Property="HorizontalAlignment" Value="Center"/>
                        <Setter Property="VerticalAlignment" Value="Center"/>
                        <Setter Property="Background" Value="#FFF"/>
                        <Setter Property="Foreground" Value="#000"/>
                    </Style>
                </Grid.Resources>
                <Grid.RowDefinitions>
                    <RowDefinition/>
                    <RowDefinition/>
                </Grid.RowDefinitions>
                <Border x:Name="mask" Background="#FFF" CornerRadius="{Binding ElementName=Buttons,Path=CornerRadius}" />
                <Button Grid.Row="0" Click="ButtonUp_Click" Content="{materialDesign:PackIcon Kind=ArrowUp}"/>
                <Button Grid.Row="1" Click="ButtonDown_Click" Content="{materialDesign:PackIcon Kind=ArrowDown}"/>
            </Grid>
        </Border>
    </Grid>
</UserControl>