C# 将2列gridview相乘，并以新的格式显示结果

我需要将列valorprod*cantidad相乘，并显示一个名为subtotal的新列

代码在这里

 DataTable dsDetalle = new DataTable("Data");
 using (MySqlCommand commandSql = cn.CreateCommand())
 {
      commandSql.CommandType = CommandType.Text;
      commandSql.CommandText = "select * from detalle where idVenta=@idVenta and idlocal=@idlocal";
      commandSql.Parameters.AddWithValue("@idVenta", txt_boleta.Text);
      commandSql.Parameters.AddWithValue("@idlocal", txtlocal.Text);
      MySqlDataAdapter sqlAdapter = new MySqlDataAdapter(commandSql);
      sqlAdapter.Fill(dsDetalle);
 }

---

您可以动态创建计算列

commandSql.CommandText = @"
   SELECT  *, ( valorprod * cantidad ) AS subtotal
   FROM    detalle
   WHERE   idVenta = @idVenta AND idlocal = @idlocal";