public void Dispose()

Public Sub Dispose

This method clears memory and delete any resources that are used by the upload object. If you do not call this method then instance of Upload class will keep in memory collection until time to life (see UploadEnvironment..::.UploadTTL) is not expired.
You can use this method to delete unnecessary Upload instances (Ex: If an exception had been thrown during upload then you can handle this error, display some message and then delete Upload instance.)