Suggestion: Add OverwriteIfNotEqual to FtpLocalExists for safer mirroring

[avsimian]

I am using the DownloadDirectory function with FtpFolderSyncMode.Mirror. It works well, but I encountered a problem (or maybe I missed something)

My use case is to mirror a directory from the FTP server, ensuring that when a file with the same name changes remotely, the local file is overwritten. However, the existing FtpLocalExists.Resume (Append) option only appends extra bytes to the local file, which can result in corrupted files.

Would implementing an OverwriteIfNotEqual option be useful for this scenario? Or is there an alternative approach that I might have missed?

[FanDjango]

FtpLocalExists.Resume (Append) option

Well, that is actually for continuing an operation that was interrupted for some reason. Given that FTP is such an ancient protocol with servers implementing this in many different qualities, this option is not my favorite, anyway.

Would implementing an OverwriteIfNotEqual option be useful for this scenario?

I suppose this might be a nice enhancement, but it would need a potentially time consuming FileCompare operation on each existing local file to make a decision - which is currently not implemented in the DownloadDirectory funtionality - it just compares a list of files.

Or is there an alternative approach that I might have missed?

IMHO

Currently I would use GetListing and a loop of the CompareFile APIs for a reliable decision on what to download (with overwrite).

The risk: Lose an outdated file on download failure. Solution for that: renaming the existing outdated file prior to download as .bak, deleting that after successful download.

And once you have coded that (I haven't needed this personally) then please submit that here for us to include as a new API, maybe?

[FanDjango]

And you should be using FtpLocalExistsMode.Overwrite anyway, with DownloadDirectory, this will always overwrite the file, no comparison is made to see if the download would be unneeded.

[robinrodricks]

@avsimian How would this work? Would you expect the CONTENTS of the files to be checked or just the date/size.