Unpublish an Item in Umbraco

//Unpublishing an Item in Umbraco
protected void ReportNewsComment(int id)
{
Document doc = new Document(id);
doc.UnPublish();
doc.Save();
umbraco.library.UpdateDocumentCache(doc.Id);
//childrens.GetProperty("subjecttoNotify").ToString()+parentNodeID.ToString())
}