I placed a support ticket and got a quick response. I hope this helps others.
RadAsyncUpload does not upload files with postback, don't you talk about
the regular RadUpload? If so, you can take a look at the following help article
information on how clear the inputs if the user has pressed button
other than the submit one.
Please, have in mind that the upload inputs are going to cleared from
the selected files, i.e after a postback they won't contain any selected
How to hold view state of selected files?
This is not possible due to a security reasons. The problem is that the
browsers do not allow you to set the value of the uploads using
order to upload random files from users computers. One must manually
select a file in order to make it appear in the input field. Currently
there is no way to workaround this issue. This is the way all modern
The good news are that we are working on a new version of the
RadAsyncUpload control that will support this (upload with specific
button only) and many more other useful features (It is going to use
Flash/Silverlight). The control is scheduled for Q2 2010.