以下是更新数据库的程序,但却不能完成更新的功能 ,问题到底出在哪里?请各位指点,谢谢!

private void Button1_Click(object sender, System.EventArgs e)
        {
            string connString=@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" +Server.MapPath(@".\db1.mdb");
            OleDbConnection conn=new OleDbConnection(connString);
                        
            string sql="UPDATE  table1 SET AGE=11111 WHERE NO=112";
            OleDbCommand cmd=new OleDbCommand(sql,conn);
            conn.Open();
            cmd.ExecuteReader();
            conn.Close();
            
            conn.Close();  
            string sql2="select * from table1";
            OleDbCommand cmd2=new OleDbCommand(sql2,conn);
            conn.Open();  
            this.DataGrid2.DataSource=cmd2.ExecuteReader();
            this.DataGrid2.DataBind();
            conn.Close();  
        }