Ok, Yurii, thanks, and here's the information you requested:
The user only read the database file and collection. There is no upload, create, or delete actions by the user.
The file collection holds the actual pdf file and the file name assigned to it ( e.g. xxxxxxfffggggg-name1.pdf).
The database also has some collections that hold specific information about each pdf file in the file collection (e.g. "Name1.pdf", which is part of the assigned Id or file name of the pdf file).
4 Information from the collection is used in the UI. When an item is clicked, its name is used to find the file in the file collection, where part of that name contains the name of the item clicked.I hope that is clearer.
In this app I have a need for 2 methods to get the desired file name in the file collection:
How to map the file name from the file collection directly to the UI
How to use code to get the file name when a part of that name is provided, as in no 4 above.