How to set number format in WPF DoubleTextBox?

<Grid>
  <syncfusion:DoubleTextBox x:Name="Double1" Width="150" Height="23" Value="1234567">
    <syncfusion:DoubleTextBox.NumberFormat>
      <numberformat:NumberFormatInfo NumberDecimalDigits="4" NumberGroupSeparator="@" Value="1234567" NumberDecimalSeparator="*"/>
    </syncfusion:DoubleTextBox.NumberFormat>
  </syncfusion:DoubleTextBox>
</Grid>

using Syncfusion.Windows.Shared;
namespace DoubleTextBox
{
  /// <summary>
  /// Interaction logic for MainWindow.xaml
  /// </summary>
  public partial class MainWindow : Window
  {
    public MainWindow()
    {
      InitializeComponent();
     DoubleTextBox doubleTextBox = new DoubleTextBox();
     doubleTextBox.Width = 150;
     doubleTextBox.Height = 25;
     doubleTextBox.Value = 1234567;
     doubleTextBox.NumberFormat = new NumberFormatInfo()
     {
       NumberGroupSeparator = "@", NumberDecimalDigits = 4, NumberDecimalSeparator = "*"
     };
    }
  }
}