public function Clear($ConversationID, $ClearingUserID) {
      $this->SQL->Update('UserConversation')
         ->Set('Deleted', 1)
         ->Set('DateLastViewed', Gdn_Format::ToDateTime())
         ->Where('UserID', $ClearingUserID)
         ->Where('ConversationID', $ConversationID)
         ->Put();

      $this->CountUnread($ClearingUserID);
   }