应用lambda表达式，返回一个具体的对象

return (from row in data.AsEnumerable()
                        select new GoodsInfoViewModel()
                        {
                            GId = row.Field<int>("Gid"),
                            GName = row.Field<string>("GName")
                        }).FirstOrDefault()

直接调用方法 FirstOrDefault()==>有数据则返回第一条，没有则返回null