The DevExpress ASP.NET File Manager (ASPxFileManager) supports virtual scrolling, which allows files and folders in file area to load on demand. In this mode, the file manager loads items automatically when the end-user scrolls the control content. Unnecessary file are unloaded.
The amount of items that are currently uploaded to the client side can be specified by the PageSize property (300 by default).
To disable virtual scrolling set the PageSize property to 0. In this case, all items contained in the current folder, are uploaded to the client side.