问无法更新access数据库引发的asp.net

EN

protected void Btnupdate_Click(object sender, EventArgs e)
    {
        foreach (RepeaterItem RI in rptEdit.Items)
        {
            Label id = RI.FindControl("Pid") as Label;
            TextBox prdname = RI.FindControl("prdname") as TextBox;
            TextBox prdprice = RI.FindControl("prdprice") as TextBox;
            TextBox prdshortdesc = RI.FindControl("prdshortdesc") as TextBox;
            TextBox prdtype = RI.FindControl("prdtype") as TextBox;
            TextBox prdbrand = RI.FindControl("prdbrand") as TextBox;

            int updated;
            string connection = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\\Table.accdb";
            using (var conn = new OleDbConnection(connection))
            {
                conn.Open();
                string updSql = @"UPDATE ProductList SET
                    Pname = '" + prdname.Text + "' WHERE Pid = ?";
                using (var cmd = new OleDbCommand(updSql, conn))
                {
                    cmd.Parameters.Add("@Pname", OleDbType.VarChar).Value = prdname.Text;
                    updated = cmd.ExecuteNonQuery();
                    conn.Dispose();
                    conn.Close();
                }
            }
        }
    }