In the SFTP protocol, there is no concept of multi-file transfers. It's in actually a simple remote file system protocol, despite its name.
This means that there is no standard way for an SFTP client to signal an "end of a multi-file transfer" to the server. In practice, if the whole file transfer process is under your control, there are numerous workaround for this - for example, the SFTP client might upload a ".done" file when all the files have been uploaded. Then, you could use
FileUploaded event to detect this.
The drawback of this is that it won't work for client's that don't behave as expected. However, because this is due to the limitation of the SFTP protocol itself, there doesn't seem to be any substantially better alternatives.