How to Copy a File that is In Use

Question

I want to provide my users with the ability to post a log file onto my server rather than requiring them to find it and email it to me.

I am using this library http://ftplib.codeplex.com/ to open an ftp session on the server and send the file. There is a bit of renaming involved but that is it.

Unfortunately the log file to be sent is actually open so I got a 'file is being used by another process' exception. This makes sense when I think about it in so far as the log is open while my app is running. I closed it but, of course, uploading is a long process. I put the upload code into a background thread so that the user may continue. However the log cannot be re-opened until the upload is complete. In the meantime there could be some event that should be written to the log.

So I am looking for a way to copy the log and then upload it. What would be the best way to do that? The log is a binary file BTW.

Answer 1

If you don't own the code that has the log file open (ie, it's another app or a closed source dll), you can try doing a File.Copy(<log>, <tempdest>) and send that file, deleting it when you're done. This only sometimes works when you don't have read access to the file.

If you do own the code that is accessing the file in the first place, you want to open it with an explicit ShareMode ie

 File.Open(path, FileMode.Open, FileAccess.ReadWrite, FileShare.Read)