用C#连接Oracle出错啦，帮小弟我看看

用C#连接Oracle出错啦，帮我看看
ORA-00936: 缺失表达式

C# code

public static int AddUsers(Users user)        {            int n = 0;            try            {                string sql = "insert into users values(id_seq.nextval,'@name',@age,'@sex');";                OracleParameter name = new OracleParameter("@name",user.Name);                OracleParameter age = new OracleParameter("@age", user.Age);                OracleParameter sex = new OracleParameter("@sex",user.Sex);                OracleCommand command = command = new OracleCommand(sql, DBHelper.connection);                command.Parameters.Add(name);                command.Parameters.Add(age);                command.Parameters.Add(sex);                DBHelper.connection.Open();                Console.WriteLine(sql);                n = command.ExecuteNonQuery();            }            catch (Exception e)            {                Console.WriteLine(e.ToString());            }            finally            {                DBHelper.connection.Close();            }            return n;        }    

C# code

string sql = "insert into users (ID,NAME,AGE,SEX) values (id_seq.nextval,:NAME,:AGE,:SEX)";