3rdpartylibs/fastreports.wpf/FastReport.Forms.WPF/CustomControls/DateTimePicker.xaml

<DatePicker x:Class="CustomControls.DateTimePicker"
             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:local="clr-namespace:CustomControls"
             mc:Ignorable="d" 
             d:DesignHeight="25" d:DesignWidth="100">
    <DatePicker.Resources>
        <Style TargetType="{x:Type DatePickerTextBox}">
            <Setter Property="Control.Template">
                <Setter.Value>
                    <ControlTemplate>
                        <TextBox x:Name="PART_TextBox"
                             Text="{Binding Path=FormattedValue,
                                 RelativeSource={RelativeSource AncestorType={x:Type local:DateTimePicker}}}" 
                                 BorderThickness="0" Margin="0,1,0,0" />
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </DatePicker.Resources>
</DatePicker>