<Grid xmlns:xcdg="http://schemas.xceed.com/wpf/xaml/datagrid">
  <Grid.Resources>
    <xcdg:DataGridCollectionViewSource x:Key="cvs_orders"
                                    Source="{Binding Source={x:Static Application.Current}, Path=Orders}">     
    <Style TargetType="{x:Type xcdg:SearchControl}">
      <Setter Property="Watermark"
              Value="Type some text here" />
    </Style>
  </Grid.Resources>
 
  <xcdg:DataGridControl x:Name="OrdersGrid"
                        ItemsSource="{Binding Source={StaticResource cvs_orders}}">   
  </xcdg:DataGridControl>
</Grid>