How to provide Prompt Lists in an NHibernate WinForms application

Question

Background

WinForms application using NHibernate. Application is in MDI style and each MDI child form opens a new NHibernate session at Load which remains open for the life of the form.

Question

My application is basically an "order management" or "purchasing" system. One particular form uses a lot of "lookup" lists. Like a list of products, a list of vendors, a list of locations, a list of UnitsOfMeasurement, a list of PriceQuotes, etc.

Lots of lists, that all get loaded when the form is constructed.

Problem: I need the lookup lists, but I need the form to be a bit faster to load. The form is taking too long to perform all the lookups. How can I get better performance and keep my lookup lists?

My Thoughts

• Can I load the lookup lists once and hold on to them for the life of the application, and periodically check to see if the lists are stale?

• Can I load just the text description for the lists, and instead of holding a bunch of IList, IList, etc, I could hold a bunch of IList, and then when I save, perform the Gets against NHibernate to get the real object.

• Is there some other approach that I just haven't thought of?

Answer 1

Are you sending lists of full objects to your UI? I recently worked on an app using DTO's between the data layer and the UI so I'm not sending the full object, just a description and an identifier. That could help you trim out some unneeded data. So basically when the screen loads a service call is made, nhibernate gets all of the objects I want for my list box, then the UI binds to the list. I bound my listbox display member to the description and the value member to the identifier.

Answer 2

You should definitely cache slowly changing data to improve performance. How often you need to check for stale data depends on the type of data and your business, e.g. units of measure probably doesn't change as frequently as a list of products. You should also provide a method for manually refreshing lists so that the user can refresh them if something appears to be missing.

If you need the business objects in the list in order to perform a database operation, you can call ISession.Lock(obj) to lock the object into the current ISession. One thing to be aware of is that the lock doesn't automatically cascade to child objects: I think there's a mapping setting to do that or you can do it manually.