Concurrent file write-access

Question

Hi, I have a web service that logs some information to a text file; this web service is invoked asynchronously by a number of client apps, and this is causing a "The process cannot access the file because it is being used by another process" error.

This is the code I am using

FileStream fs = new FileStream(filename, FileMode.Append,
_FileAccess.Write, FileShare.Write);

writer = new StreamWriter(fs);
...
writer.Close();

No other code is accessing that file. Am I missing something?

Marco · Answer

I would rather write to the Win Event Log or to a Database, but we need to have a CSV output with a specific schema and we don't have any DB instance we can use at the moment.

Ryan Alford · Answer

is it a requirement to write to a file? writing to the server's event log would not cause this problem.

Marco · Answer

Hi, I have tried the Mutex class (having a different Mutex instance referring to the same Mutex name for each Web Service instance) but that didn't help - for some reason, with concurrent Web Service requests the Mutex goes into deadlock (as well as slowing down greatly the application execution). Is there any way to share a file for writing? I don't care about the order the data is written to the file, just that each write operation is atomic and does not stop the others. Thanks

Sunny Chen · Answer

Did you have a try on the Mutex class? using System.Threading; Mutex mutex = new Mutex(); mutex.WaitOne(); // Do your job here mutex.ReleaseMutex(); I don't know if this helps in your scenario, you can have a check. Hope this helps.