There are some already known limitations of RadProgressArea
. One of them is that the cancelling of the upload is not supported in Safary and, respectively, in Google Chrome.
There is more detailed information on the subject available in the following link: RadProgressArea Known Limitations
Additionally, there is an available built-in AsyncUpload functionality in RadFileExplore where the progress monitoring is done in real time with no need of additional customizations (the cancelling of the upload is working properly in there). In order to enable it the EnableAsyncUpload property must be set to true.
the Telerik team
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 their blog feed