Processing variable number of form fields

Question

I am working on a form which displays information about orders. Each order has a unique id, but they are not necessarily sequential on the form. Also, the number of fields can vary (one field per row on the form). The input into the form will not be mapped straight into the database, but will be added to the current value in the database, and then saved. An example of the form is in the picture below - the callout on the right shows the id for each row.

I know how to generate the form like this, but I can't work out how I can easily process each of these rows reliably. I also know how to give each of the fields a unique identifier, like name="order-23" or name="order[23]", but how can I translate that name so that I can update the related record in the database?

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EDIT: One solution I can think of would be to iterate through every form field in the FormCollection, and if the name of the field matches the pattern, then I will extract the number from that field-name and process it.
However, I feel that there must be a much easier way to go about it - this method would likely involve a fair bit of string processing on each field, and there would possibly fall over if I have to add extra fields for each row later on.

Answer 1

Don't you have a list of IDs after postback? I believe you should not depend on what IDs are actually sent from the form, as anybody could change the IDs on the form to whatever they want, so it's a security issue. So you should after postback have a list of IDs you want to update (the same list you used to create the form with). In that case, you know exactly what id string you should use to retrieve the value from FormCollection.

In case you really can't get the list of IDs you are going to update, just use the FormCollection iteration as you suggested in your comment. The string processing is not that expensive in comparation with all other stuff being done at request processing.