public Comment getEntity(File file)
 {
     Comment comment = new Comment();
     comment.file = file;
     comment.serverCommentID = commentid;
     comment.authorName = author;
     comment.content = content;
     return comment;
 }
 // Called during a remove operation
 private void detach_comment(Comment comment)
 {
     NotifyPropertyChanging("comment");
     comment.file = null;
 }
 // Called during an add operation
 private void attach_comment(Comment comment)
 {
     NotifyPropertyChanging("comment");
     comment.file = this;
 }