What are design patterns to support custom fields in an application?

Question

We develop a commercial application. Our customers are asking for custom fields support. For instance, they want to add a field to the Customer form.

What are the kn

Answer 1

I am currently working on a project with this same problem, and I have chosen to use option 3, but I added a FieldType field and a ListSource field in case the FieldType="list". The ListSource field could be a query, an sql view, a function name, or something that results in a list of options for the list. The biggest problem with trying to store fields like this in my situation is that this field list can change, and the users are allowed to edit the data later. So what to do if the field list has changed and they go to edit. My solution to that scenario was to allow editing only if the list hasn't changed and to display read-only data if it has.