When the RadUpload tries to open (read) the selected file and access is not allowed, the file will be ignored and will not be uploaded. You would see an error icon next to the file in the control. There is nothing we could do until the other process releases the file. You could iterate through the RadUploadItems in the Items collection of the Upload control and check their ErrorMessage property. If there is one with this exception, then you could try to open the file or prompt the user to close it before uploading.
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