The RadUpload control is an ASP.NET component. It is designed to support different browsers without the need to install third party components in your browser such as ActiveX and Flash. Multiple file selection or folder selection options in one "Choose file" dialog are restricted from the browsers and we cannot
do anything to workaround the problem without
sacrificing the cross-browser compatibility.
If you have other questions, do not hesitate to contact us again.
the Telerik team