MDI windows in a ribbon window - having issues

private void button1_Click(object sender, ExecuteRoutedEventArgs e)
        {
            
          ActiproSoftware.Windows.Controls.Ribbon.Controls.TextBox content = new ActiproSoftware.Windows.Controls.Ribbon.Controls.TextBox();
          string name = "MyDocumentWindow1"; string title = "Document Window" +DateTime.Now;

          BitmapImage image = new BitmapImage(new Uri("/Images/Test.png", UriKind.Relative));
          wdwAbout mycontent = new wdwAbout(); // wdwAbout is a ribbon window with a ribbon
          DocumentWindow window = new DocumentWindow(dockSite,name, title,image ,mycontent );
         
          window.Activate(true);
                     
        }