even more thread problems: error catching

[dreamdelerium]

so, heres my issue: i have a thread that runs a function to check a wireless modem to see if theres any new sms's. every thing seems to be going well but i need to plan for the eventuallity that someone will be unplug the modem. unfortunatly, i cant seem to catch the resulting error. heres what i got:

Public Sub BackgroundWorker1_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        Dim j As Integer = 0
        Dim i As Integer = 0
        Debug.Print("bg worker begin")
        While i = j

            If BackgroundWorker1.CancellationPending Then
                i = 2
                e.Cancel = True
                BackgroundWorker1.Dispose()
                Debug.Print("bg worker middle")
                Exit While
            Else
                CheckForNew()
            End If
        End While

        Debug.Print("bg worker end")
    End Sub

and heres the functio it calls:

 Public Sub CheckForNew()

        Debug.Print("checkfornew begin")
        Dim storage = getMessageStorage()
        Dim MsgLocation As Integer
        Dim counter As Integer = 0
        Try

            If isPortAModem() = True Then
                comm = New GsmCommMain(Microsoft.VisualBasic.Right(GetPort, 1))

                comm.Open()
                counter = 0
                Try
                    Dim messages As DecodedShortMessage() = comm.ReadMessages(PhoneMessageStatus.ReceivedUnread, PhoneStorageType.Sim)


                    If (messages.Length.ToString()) = 0 Then

                    Else

                    End If

                    For Each DecodedShortMessage In messages
                        MsgLocation = DecodedShortMessage.Index

                        ShowMessage(DecodedShortMessage.Data)


                        counter = counter + 1
                        comm.DeleteMessage(MsgLocation, PhoneStorageType.Sim)
                    Next


                Catch ex As IOException
                    MsgBox(ex.Message)
                Finally

                End Try
                Try
                    comm.Close()
                Catch ex As IO.IOException

                End Try


            Else
            End If
    Debug.Print("chekcfornew end")

        Catch ex As Exception

        End Try
    End Sub

this function is called every second for the durration of the programs life (it check to new txt messages). i beleive the error is comming from the .open command. i also believe that because its on a different thread, the try..catch statemenst arent working properly (am i right?). the errorr thats not being caught can only be seen durring debug (durring run time of the application, the program just crashes with no error).

how do i catch this

[kleinma]

do you know what type of exception is being thrown? You are catching IOException only, so if the exception is of some other type, or even of the base exception type, you won't catch it.

I would try changing your code to "Catch Ex as Exception" instead, even if its just to test so you can see the exact type of exception being thrown, and then you can catch that one specifically too.

You do have a regular catch ex as exception at the very outside of your code, which should catch the exception if it bubbles up that far, however you also don't actually handle it, you just catch it, so the app is basically just swallowing any exception at that point and acting like it ran fine...

Try/Catch blocks can have multiple catch statements.

Try
   'code here
Catch Ex as IOException
   'handle IO Exception
Catch Ex as Exception
   'handle any other exception
End Try

[dreamdelerium]

yeah, it is an ioerror but ive tried using just "capture ex as exception". it gets by anyway. could it be be cause its running in a seperate thread?

[kleinma]

I don't think so really.. your error handling is in the same routine that is in the seperate thread, so it should work.

If you take out all your error handling, do you see the exact place the code hits the exception?

You could also try adding try/catch blocks in the actual DoWork routine, and see if you get any different behavior then.

[dreamdelerium]

yeah, thats another problem. when the error pops, it doesnt hi light the part of code thats causing the error, as it normally does.