a dog in the manger是个名词性短语，常与系动词连用，充当表语（主语补足语）eg: He borrowed a lot of books from the library, but he didn\'t read a book. He was really a dog in the manger.
There are some officials who are only the dogs in the manger.
Smith was a dog in the manger over that roll of wire; it was no use whatever to him, but he wouldn\'t let us have it.