Can't get checking if file exists using textboxes to work - vb.net

Question

I've been racking my brain for days over this code and I just can't seem to get it working. I've researched and researched with no luck. I have four textboxes on my form. Two textboxes is a folder location and the other two textboxes are file locations. I'm trying to use a function that will return true or false telling if the files in the two textboxes exist or not. I don't see anything at all wrong with this code and it just won't work! I'm sure it's something simple I'm overlooking. Maybe someone else can spot it!
Private Function doesFileExist(folderPath, fileName) As Boolean
If IO.File.Exists(folderPath & "\" & fileName) Then
Return True
Else
Return False
End If
End Function
Private Sub chkStart_CheckedChanged(sender As Object, e As EventArgs) Handles chkStart.CheckedChanged
If doesFileExist(txtCPU.Text, txtFileCPU.Text) And
doesFileExist(txtGPU.Text, txtFileGPU.Text) Then
If chkStart.Checked Then
chkStart.Text = "Stop Monitor"
Else
chkStart.Checked = False
chkStart.Text = "Start Monitor"
End If
Else
chkStart.Checked = False
MessageBox.Show("Please check directory & file locations!", "Error!", MessageBoxButtons.OK)
End if
End Sub
I want to mention that before I tried nested if statements on this I also tried to separate them both like so..
Private Sub chkStart_CheckedChanged(sender As Object, e As EventArgs) Handles chkStart.CheckedChanged
If Not doesFileExist(txtCPU.Text, txtFileCPU.Text) And
Not doesFileExist(txtGPU.Text, txtFileGPU.Text) Then
chkStart.Checked = False
MessageBox.Show("Please check directory & file locations!", "Error!", MessageBoxButtons.OK)
Exit Sub
End If
If chkStart.Checked Then
chkStart.Text = "Stop Monitor"
Else
chkStart.Checked = False
chkStart.Text = "Start Monitor"
End If
End Sub
Both of these ways will show the messagebox if the application is ran with the checkbox checked on start up. Not only will it show the messagebox it also shows the messagebox twice! I've yet to figure that one out!

Answer 1

Your check file exists can be simplified... (It's been a while since I used VB so apologies for any syntax errors, I don't have an IDE to hand)
Function DoesFileExist(Folder as String, Filename As String) As Boolean
Return IO.File.Exists(IO.Path.Combine(Folder, Filename))
End Function
Re: Changing whether the "check" checkbox is set shouldn't perform the check itself - otherwise you only check when people click. (Incidentally, I'm guessing you're getting a message twice as code elsewhere ticks/unticks this checkbox, but it's only a guess).
Private Sub chkStart_CheckedChanged(sender As Object, e As EventArgs) Handles chkStart.CheckedChanged
If chkStart.Checked Then
chkStart.Text = "Stop Monitor"
PollTimer.Start()
Else
chkStart.Text = "Start Monitor"
PollTimer.Stop()
End if
End Sub
Finally... You need to define when your check will happen. Ideally, you'd want to use a FileSystemWatcher which will give you events when the file system changes, but you can also poll using a timer...
Private PollTimer As System.Timers.Timer
Then in your Form Main, do some initial timer setup...
...
PollTimer = New System.Timers.Timer()
PollTimer.Interval = 30000 ' Seconds
AddHandler PollTimer.Elapsed, AddressOf CheckExistsNow
PollTimer.Start()
...
And finally the code to run every time we want to make the check....
Sub CheckExistsNow(sender As Object, e As System.Timers.ElapsedEventArgs)
If Not DoesFileExist(txtGPU.Text, txtFileGPU.Text) Then
' Handle the missing file.
End if
End Sub