What will be the exception code for a service crash?
I have created a WPF service for tracking a user session, while tracking the user session I also want to track a event of service crash. For that I have been checking the windows event log and identifying the error. But I am confused, It was showing a error there which tells that failed to process a sessionchange! Is that a service crash?? Is there any specific exception code for a service crash/ Can anyone help with suggesting relavent articles/ points for identify a system crash?
Not a crash, you are just seeing the .NET framework's ServiceBase class doing its job. In a few specific cases it will catch an exception and create an entry in the application event log. In does so in its code that causes the OnStart(), OnStop(), etcetera method to run.
Looks like the service's OnSessionChange() method fell over, just a bog-standard file locking error. In all likelihood the service code is a bit clumsy, it needs to open that file in its Main() method so nobody else can mess with it. Probably wasn't tested really well, OnSessionChange() does not fire very often. And certainly little reason to try to log anything, but who knows.
This should not otherwise affect the service process, the service control manager doesn't give much of a hoot if the OnSessionChange notification fails. Nothing it can do about it. So you are seeing this mostly because you started looking, services do tend to misbehave without anybody noticing. It just isn't very visible that they do. Do make sure it wasn't your code that put a lock on the Log.txt file. If you do then you'll have to use FileShare.ReadWrite to prevent the service from falling over.