Create a “virtual directory” or tree view so that user can browse through files that exist in a database?

I know I can browse through files when they exist by using a FileDialog. I am tracking the changes that are made in a directory and every time there has been a change I save that file in a database. I record the file path, date modified, date entered to the database and a file id to identify each file.

So my database contains a big list of files (about 50,000). When I browse through a file I place that list of files in a listview. If I want to recover a file I would have to browse through that listview which is not hard because I have added a search feature in order to filter results.

But I would like to enable the user to browse through the file just as you would do it in Windows. In other words you would have to double click a folder in the listview to see its contents. I managed to do that by creating an event that when you double click a folder in the listview it will just show the files which parent directory is the one that has been double clicked.

In other words by double clicking a folder you will see the contents of that directory. The only problem with this technique is that it is slow. Every time double click on a folder it takes about 2 seconds.