For UWP, it is easy to get all files in the app local folder as:
IReadOnlyList
var storageFolder = await ApplicationData.Current.LocalFolder.GetFolderAsync("Assets");
var files = await storageFolder.GetFilesAsync();
https://docs.microsoft.com/en-us/uwp/api/windows.storage.applicationdata
You can access you installation folder by using Package.InstalledLocation. Therefore your code can look like this:
StorageFolder appInstalledFolder = Windows.ApplicationModel.Package.Current.InstalledLocation;
StorageFolder assets = await appInstalledFolder.GetFolderAsync("Assets");
var files = await assets.GetFilesAsync();