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())
}