数据库更新查询出错

我的系统不会更新，它显示这个错误，我不知道该怎么办。有什么建议吗?这是我的代码

 private void btnupdate_Click(object sender, EventArgs e)
    {
        com.Connection = con;
        con.Open();

       string query = "UPDATE [Promissory] SET [pdate] = ?,[Edpno] = ?, [gradingperiod] = ?, [pamount] = ?, [reasons] = ?, [syid] = ? WHERE Promissoryno = ?";
        var accessUpdateCommand = new OleDbCommand(query, con);
        accessUpdateCommand.Parameters.AddWithValue("pdate", txtdate.Text);
        accessUpdateCommand.Parameters.AddWithValue("Edpno", txtedpno.Text);
        accessUpdateCommand.Parameters.AddWithValue("gradingperiod", txtgradeperiod.Text);
        accessUpdateCommand.Parameters.AddWithValue("pamount", txtamount.Text);
        accessUpdateCommand.Parameters.AddWithValue("reasons", txtreasons.Text);
        accessUpdateCommand.Parameters.AddWithValue("syid", txtsyid.Text);
        accessUpdateCommand.Parameters.AddWithValue("Promissoryno", txtpromiseno.Text); // Replace "123" with the variable where your ID is stored. Maybe row[0] ?
        da.UpdateCommand = accessUpdateCommand; //This line here is the error
        da.UpdateCommand.ExecuteNonQuery();

        con.Close();
}

com.Connection = con;