Database Application Design Recommendations?

The main purpose of the my app that I need your help with is, to deliver an always (or close to) up to date a list of files for the user to choose from for a variety of common purposes. For instance, opening the selected file in its native client editor application so the user can make changes. Another purposes would be to print the file, and I have others.

If nothing else (meaning recommendations for a better design that still keep my desired in mind) I'd like ideas on how to update my complex DataSet (background processing options, what's the most efficeient/quickest way to update my DataSet) as the list of files changes while my app is running and my app is designed to never close due to the long amount of time it take to load it initially.

The list must be always kept up to date while my app is running because not only the intial loading of data takes a lot of time but updates (new/modified/deleted) could potentially take too long depending on not only how much data to update/add (new files) but how efficeient my code is in updating the list. To be perfectly clear: If a new file is created then it need to be somehow (automatically preferably or manually i.e. button code) add to the list. If a file is deleted then it needs to bet removed from the list. And if the file has changed, perhaps some of it metadata or thumbnail image have changes so update the file's data in the list. All of which (new/modified/deleted) need to be as real-time as possble without degrading the server too much and without the user waiting more than a handful of seconds.

Listing all the files as quick as possible whether that be with or without metadata initially is very important because most of the time the user is going to filter (or scroll the list by typing) for a partial file name. Once the user filters/scrolls to the desired file there's a very good chance that he/she isn't even interested in the metadata, most of the time the user wants my app to open the selected file in its native client editor application so he/she can view or modify the file. The initial
load time of the data doesn't concern me as much as updates because the user can possibly do other things while it initially loads all the data as long as it not too long (more than a few minutes). From there the updates will either be automatic if possible (most desirable from a users standpoint) or the user initiated (e.g. button). Plus I'm thinking the updates might need to be done with a few different background processes (multiple threads) because I think I need one for periodic updates (e.g. every
15 minutes) and one background process for page updates meaning whatever the user has either scrolled to or filtered for, more accurately all files currently display to the user will be systematically update in the background so the user can still operate my app.

I'm currently using SqlDataAdapter.Fill to fill a DataSet object variable (which is bound [BindingSource] to a DataGridview control) to first populate the DataSet from the SQL query and then prorgammatically adds records (DataRow) for local files but please make recommendations. I don't mind big changes or starting over if necessary, I just want the best app possible based on the aforementioned criteria. I'm not sure if it complicates matters but I've also added custom columns in the DataSet for some special needs (thumbnail of files, booleans for tracking custom statuses). For the local files I'm currently populating the DataSet prorammatically (iterating a path/file string collect made by System.IO.Directory.GetFiles) since the list is first (and very quickly) populated with Vault files (which is always a far larger list than the local files) so . Again, I don't have to take this direction, make recommendations.