FileExplorer is the control, used to list files and folders inside the RadEditor's ImageManager. In order to add custom columns to it, you will need to enable the RadEditor's ExternalDialogsPath property
, modifying the FileBrowser dialog in the way, described in the mentioned by Jayesh live demo
. You might also find useful information regarding how to add code behind to a RadEditor's dialog in this KB article
I would suggest you, though, to contact the DNN support for more detailed information on how this changes could be done in the DNN Editor, which is the exact version of the control from which you should take the External dialogs files and where these files have to be placed.
I hope this information would be helpful for you.
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to the blog feed