This exception is usually raised when the control can't reach the specified UploadHandler
and the upload session cannot complete. However, in your case I'm not sure why some attempts to reach the handler as successful while others aren't. Can you try deploying the application in a different server as we feel that the settings of a Windows Server 2008 R2 may be the cause for the issue.
If this isn't an option for you, you can change the definition of the RadUpload
control to specify an absolute path to the RadUploadHandler
(setting an absolute path as the value of the UploadServiceUrl
However, if both of these suggestions don't work for you, you can reattempt the upload by implementing a logic for clearing the session and restarting it when the upload fails, like this:
sender, FileUploadFailedEventArgs e)
RadUpload upload = sender
List<RadUploadSelectedFile> SelectedFiles =
I hope these suggestions will help you get over the issue. Please let us know how it goes.
the Telerik team
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