vb.net timer and exception (try... catch) and memory leak - vb.net

Question

Scenario:
I've hundreds of applications instances running on client machines doing a certain job. Something like a cloud app.
Objective: When an error occur in any of them i want to report the error to an error-log database an quit silently the app to avoid user annoyance.
The problem:
I've migrate to VB.NET recently and don't know yet wich is the best aproach to error handle the code. Those instances are runing a routine under a timer.
Private Sub timerLifeSignal_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles timerLifeSignal.Tick
MAINSUB()
End Sub
Friend Sub MAINSUB()
frmSAN.timerLifeSignal.Enabled = False
...
'do the job
...
frmSAN.timerLifeSignal.Enabled = True
end sub
At first glance i've put try/catch into every single function but it leads to a memory leak since, AFIK, the exception object created was not disposed correctly.
So is there a way to make try/catch do not memory leak under these circumstances?
Thx,
UPDATE:
Basically what i was doing is something like:
Private Sub timerLifeSignal_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles timerLifeSignal.Tick
MAINSUB()
End Sub
Friend Sub MAINSUB()
Try
frmSAN.timerLifeSignal.Enabled = False
...
'do the job
...
frmSAN.timerLifeSignal.Enabled = True
Catch ex as Exception : gERRFUNC(" | MAIN | " & ex.Message) : End Try
end sub
friend sub dothejob
try
...
' really do the job
...
Catch ex as Exception : gERRFUNC(" | MAIN | " & ex.Message) : End Try
end sub
and so on... and finally (may here it's my mistake) another try/catch nested into here:
Public Sub gERRFUNC(Optional ByVal errorMSG As String = "")
Try
' log message on database
SQL = "INSERT INTO sanerrorlog VALUES (NULL, '" & currentMySQLTime() & "', '" & errorMSG & "');"
' function that open conn and execute the sql... working fine
' NOTE THAT INSIDE THE DORS FUNCTION THERE'S ALSO A TRY/CATCH USING THE SAME EX OBJECT.
DORS(SQL)
' clean up things
SQL = "DELETE FROM sannie WHERE sid=" & gMyID
DORS(SQL)
For i = 0 To UBound(gCONN)
If gCONN(i).State = ConnectionState.Open Then gCONN(i).Close()
Next
frmSAN.nfi.Visible = False
gWWB = Nothing
End
Catch E As Exception: End: End Try
End Sub
So... if i do this:
Private Sub timerLifeSignal_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles timerLifeSignal.Tick
Try
MAINSUB()
Catch ex as Exception : gERRFUNC(" | MAIN | " & ex.Message) : End Try
End Sub
Means all exceptions inside mainsub should be catched?

Answer 1

You have another way..
You can attach events to the app domain and main thread, in case it fails, to catch the errors.
Something like:
AppDomain.CurrentDomain.UnhandledException +=
CurrentDomain_UnhandledException;
Application.ThreadException +=
Application_ThreadException;
Application.ApplicationExit += Application_ApplicationExit;
with this in mind, every time an exception occurs, anywhere that it hasn't a catch by itself, will fall trough any of this ones...

Answer 2

Try/Catches by themselves don't cause memory leaks. Not finalizing something after a failure, which triggers a catch can however. By removing your try/catches, you've apparently exposed something else that does finalize, even though informally, the object which was causing a memory leak.
Ask yourself this, how could a directive in your code cause a memory leak? Try, nor Catch are references to an object, and thus could not cause memory consumption issue by themselves -- only by the logical path of the code they control.

Answer 3

Just for reference the memory leak problem occurs because of nested try/catch loops wich (by my mistake) uses the same variable as exception object.
To be more clear take the following example:
Public Sub gERRFUNC(Optional ByVal errorMSG As String = "")
Try
// do something wrong here
Catch E As Exception: gERRFUNC(ex.Message): End Try
End Sub
friend Sub gERRFUNC(msg as string)
Try
// call another external sub (wich eventually may also throw an execption)
// take note that the var 'E' is also referenced here and everywhere
// so as 'E' is set it enters on a Exception loop causing the 'memory leak' problem.
Catch E as Exception: End: End Try
End Sub
By removing the nested try/catch or by using a well structured error 'flow' may avoid these type of problem.
Best Regards,
Paulo Bueno.