How Do I Add A Stackpanel To An Expander Header Via Code

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C#

WPF

I am generating expanders via code (not xaml) and i would like to have the header contain a stackpanel. I know this is possible as i have allready done it in xaml. I followed the following msdn tutorial:"The article" . I then inserted a stackpanel in the bulletdecorator.

But instead of displaying the contents of the bulletdecorator my expander header is showing "System.Windows.Controls.Primitives.BulletDecorator". How can i achieve this? At the end my expander header should contain some text and a datagrid with 1 row of data (the sum of the underlying datarows)

here is a code snippet:

//Create containing stack panel and assign to Grid row/col
            Grid.SetRow(ParentPanel, 0);
            Grid.SetColumn(ParentPanel, 1);
            StackPanel InnerSTack = new StackPanel();
            //Create Expander object
            Expander exp = new Expander();
            exp.HorizontalAlignment = System.Windows.HorizontalAlignment.Left;
            exp.IsExpanded = true;
            exp.Width = ParentPanel.Width;
            //and the bulletdecorator with the datagrid 
            System.Windows.Controls.Primitives.BulletDecorator bp = new System.Windows.Controls.Primitives.BulletDecorator();
            Image im = new Image();
            BitmapImage bi = new BitmapImage();
            bi.UriSource = new Uri(@"pack://application:,,/images/icon.jpg");
            im.Source = bi;
            im.Width = 10;
            bp.Bullet = im;
                TextBlock tb = new TextBlock();
                tb.Text = TN.Text;
                tb.Margin = new Thickness(20,0,0,0);
                InnerSTack.Children.Add(tb);
                bp.Child =  InnerSTack;
             exp.Header = bp;