ORA-01036: 非法的变量名/编号

最近写程序时，往Oracle中插入数据，出现错误ORA-01036:非法的变量名/编号，代码如下：

DbConnection conn = GetCon();
            conn.Open();
            DbCommand cmd = conn.CreateCommand();
            string sqlrt= "insert into T_User(Id,Name,Password,E_Mail) VALUES(@id,@name,@password,@email)";

                cmd.CommandText = sqlrt;
                cmd.Parameters.Add(new SqlParameter("@id", Convert.ToInt32(txtId.Text)));
                cmd.Parameters.Add(new SqlParameter("@name", txtName.Text));
                cmd.Parameters.Add(new SqlParameter("@password", txtPassword.Text));
                cmd.Parameters.Add(new SqlParameter("@email", txtEmail.Text));
            int num = cmd.ExecuteNonQuery();
 …………………………………………………………………………

原作者：http://www.verydemo.com/demo_c158_i59092.html