Question

what is the best way to load dropdown lists from reference/lookup tables for a desktop application?

the application is layed out into 3 tiers. I’ve built up my entities.

the front end has a form with 6 tabs. and one big save (another discussion 🙂

Should I load them all when the form is initially loaded? Are there any caching mechanisms I could use?

it is vb.net app on a network drive that is accessed by several users.

it’s also worth noting that some reference tables may be updated. Via another form.

thanks
T

Answer 1

Lots of factors. One you need to populate in constructor so the data is there to populate the visual elements. Beware that just because a tab is not visible does not mean it is not loaded when you app starts.

For a static list of strings

    public class Library : INotifyPropertyChanged
    {
        private List<string>  dropDown1;

        public List<string> DropDown1 { get { return dropDown1; } } 

        public Library()
        {
            // use data reader to populate dropDown1
        }
    }

I know this will get comments that can use something lighter than a List but List has a lot of nice features, easy syntax, and easy to populate. As a next step you could structure as a client server and use some static so the list is populated once and then shared by all. If you have more properties then substitute string with a class. For a dynamic list then in the get you grab the current data from the table on demand. In your get you could hold on to the last list and if the next request is within X seconds then return stale data. It depends on if stale data is acceptable.

There are many other approaches and I do not pretend this is the best. Just putting out a relatively simple example to get you started.

When it gets to hierarchical then things get a little more complex. There you can use ADO.NET table to store the static dependent data and then apply a filter on a view.