I have an update program that is completely independent of my main application. I run the update.exe to update the app.exe. To check to see if the file is in use, I move it to another file and catch an error if it is in use. If no problems occurr I rename it back. At least that was my plan...
Main program: app.exe
Update program: update.exe
This program is used over the network without any services running. So, the users is quite literally running the exe over the network on thier machine.
I need to update the app.exe when the update.exe has run. To check to see if the app.exe was still in use I was wrapping the following in a try/catch to see if it failed:
IO.File.Move(upddir & "\app.exe", upddir & "\app.exe.tst")
IO.File.Move(upddir & "\app.exe.tst", upddir & "\app.exe")
The funny thing is, even if the app.exe is running, the move can rename it to the app.exe.tst without any error. I can even continue on in the application without any errors.
I thought I was out of my mind, so I had another programmer look at this and he verified what I said above.
So, we tried this wrapped in a try catch:
Dim readfile As New FileStream(upddir & "\app.exe", FileMode.Open, FileAccess.Read, FileShare.None)
readfile.Dispose()
I put the fileshare as none that, at least I thought it would, show that there was someone in the file.
It still continued without any error.
Anyone know why I can rename a file in use? Also, is there a better way to do this than what I am doing now?
Thanks! Eroc
The same code using "using" :)
What you could do is replace the target application with a caretaker exe.
This caretaker then spawns the target application, but also creates a locked file in a shared location. The lock is released and the file is deleted when the app exits.
Then, before you update the app.exe, you check are there any locked files in the shared location, if there are locked files then the app.exe is in use.
The caretaker program could be a window-less application, the following console app does pretty much what it needs to do
The updater then looks for all "AppLock_*" files, and attempts to open them with a write lock, if it can't get a write lock on one of them, the exe is in use.
Hope this helps.
You could do the following to check if the application has other instances running:
Which is a more appropriate way of checking if the app is running.
Have a look at File.Move MSDN documentation. It details what exceptions are thrown. You are allowed to rename an exe even if it is in Use in Vista.
This is what I ended up doing. The network scan did not work on a peer-to-peer network. It didn't resolve the other computers at all.
Anyhow, here it is:
Hope this helps the next person.