/// <summary>
 /// Handles the Click event of ButtonOk object.
 /// </summary>
 private void buttonOk_Click(object sender, EventArgs e)
 {
     if (numerationDefinitionsListBox.SelectedItem != null)
     {
         OpenXmlDocumentNumbering numbering = (OpenXmlDocumentNumbering)numerationDefinitionsListBox.SelectedItem;
         if (_documentVisualEditor.SetParagraphNumeration(_documentEditor, numbering, 0))
         {
             _documentEditor.Dispose();
             _documentEditor = null;
             _documentVisualEditor.OnDocumentChanged();
         }
     }
     DialogResult = DialogResult.OK;
 }