Controls.DatePicker.xaml

<ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
 
                    xmlns:controlzex="urn:controlzex"
                    xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
        >

    <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="pack://application:,,,/MahApps.Metro;component/Styles/Controls.Shared.xaml" />
    </ResourceDictionary.MergedDictionaries>

    <Style x:Key="MahApps.Styles.DatePicker" TargetType="{x:Type DatePicker}">
        <Setter Property="Background" Value="Blue" />
        <Setter Property="BorderBrush" Value="{DynamicResource MahApps.Brushes.TextBox.Border}" />
        <Setter Property="BorderThickness" Value="1" />
        <Setter Property="CalendarStyle" Value="{DynamicResource MahApps.Styles.Calendar.Base}" />
        <Setter Property="ContextMenu" Value="{DynamicResource MahApps.TextBox.ContextMenu}" />
        <Setter Property="FontFamily" Value="{DynamicResource MahApps.Fonts.Family.Control}" />
        <Setter Property="FontSize" Value="{DynamicResource MahApps.Font.Size.Content}" />
        <Setter Property="Foreground" Value="{DynamicResource MahApps.Brushes.Text}" />
        <Setter Property="IsTodayHighlighted" Value="True" />
        <Setter Property="MinHeight" Value="26" />
        <Setter Property="Padding" Value="4" />
        <Setter Property="SelectedDateFormat" Value="Short" />
        <Setter Property="SnapsToDevicePixels" Value="True" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type DatePicker}">
                    <Grid x:Name="PART_Root">
                        <Border x:Name="Base"
                                Background="{TemplateBinding Background}"
                                BorderBrush="{TemplateBinding BorderBrush}"
                                BorderThickness="{TemplateBinding BorderThickness}"
                                SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />

                        <Grid x:Name="PART_InnerGrid" Margin="{TemplateBinding BorderThickness}">
                            <Grid.ColumnDefinitions>
                                <ColumnDefinition x:Name="TextColumn" Width="*" />
                                <ColumnDefinition x:Name="ClearButtonColumn" Width="Auto" />
                                <ColumnDefinition x:Name="ButtonColumn" Width="Auto" />
                            </Grid.ColumnDefinitions>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto" />
                                <RowDefinition x:Name="ButtonRow" Height="*" />
                            </Grid.RowDefinitions>

                            <DatePickerTextBox x:Name="PART_TextBox"
                                               Grid.Row="1"
                                               Grid.Column="0"
                                               Margin="0"
                                               Padding="{TemplateBinding Padding}"
                                               HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}"
                                               VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}"
                                               CaretBrush="{DynamicResource MahApps.Brushes.ThemeForeground}"
                                               ContextMenu="{TemplateBinding ContextMenu}"
                                               Focusable="{TemplateBinding Focusable}"
                                               FontSize="{TemplateBinding FontSize}"
                                               Foreground="{TemplateBinding Foreground}"
                                               SelectionBrush="{DynamicResource MahApps.Brushes.Highlight}">
                            </DatePickerTextBox>

                          

                
                        </Grid>

                    </Grid>


                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Setter Property="Validation.ErrorTemplate" Value="{DynamicResource MahApps.Templates.ValidationError}" />

    </Style>
</ResourceDictionary>