Question

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

Answer 1

You could do the following to check if the application has other instances running:

Process.GetProcessesByName("app.exe", "Machine1").Length > 0

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.