Hello,
This is not normal - the file explorer should call the DeleteFile method when you select a file and chose Delete from the context menu. See if this happens with the default content provider as well. If it does - then send us a simple page where we can see the problem. If the default content provider is OK, then the problem is in the way you create the DirectoryItem and FileItem objects in your custom content provider. Double-check the information for custom content providers in our online documentation:
http://www.telerik.com/help/aspnet-ajax/radfileexplorer-custom-filebrowsercontentprovider.html
http://www.telerik.com/help/aspnet-ajax/telerik.web.ui-telerik.web.ui.widgets.directoryitem-_ctor.html
http://www.telerik.com/help/aspnet-ajax/telerik.web.ui-telerik.web.ui.widgets.fileitem-_ctor.html
All the best,
Lini
the Telerik team