Serial Port - How To Use "Invoke" On The Second Thread

8 May 2006 8:29 AM

SatCom

Hello,
I had originally posted this in the winforms.controls discussion, forgive
the double post, Here is where I need help...

I have been porting some VB6 to VB2005 and here is the issue with the serial
port.
I am looking to update controls on the main form (textbox, listbox, etc)
when a call comes in. I can retrieve the ring status, caller-id etc, but
when I go to update a textbox, I receive a threading exception issue. As I
understand it, the "datareceived" event is raised on a second thread so I can
not directly update controls on the main form or (first thread) without using
INVOKE. My question is How do I do that?

Private Sub m_CommPort_DataReceived(ByVal sender As Object, _
          ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles
m_CommPort.DataReceived
        Dim strModemRecBuffer As String = ""
        strModemRecBuffer = m_CommPort.ReadExisting
....
....Extract the data from the string
....
....I realize this next line is the (Thread exception) since the control is
on the main form.
txtIncomingCall.text = strModemRecBuffer(index)

So how do I use invoke to update the controls on the first thread?
Any help would be appreciated Thanks,

SatCom

8 May 2006 1:17 PM

Fred Hedges

The best way is to create a method to call on the main thread and then
invoke a delegate to it on the other thread. For example, create a delegate
in your secondary thread and a method to execute the delegate. Ensure your
second thread has a reference to the main form instance (or some other
control come to think of it)......

Private Delegate Sub DoSomething_Delegate(ByVal theParameter1 As String,
theParameter2 as integer, theParameter3 as MyThing)

.... and then....

Public Sub Invoke_DoSomething(ByVal theParameter1 As String, theParameter2
as integer, theParameter3 as MyThing)

    Dim Parameters(2) As Object

    Parameters(0) = theParameter1
    Parameters(1) = p
    Parameters(2) = theParameter3

    Try

        m_AnInstanceOftheFormToInvokeOn.Invoke(New
DoSomething_Delegate(AddressOf m_Manager.Form.DoSomething), Parameters)

    Catch ex As Exception

            ' It didneee work.

    End Try

End Sub

.... finally, on your main form, you need a method, DoSomething:

Public Sub DoSomething (ByVal theParameter1 As String, theParameter2 as
integer, theParameter3 as MyThing)

End Sub

Now, at least this was the .NET 1.1 way of doing things. No doubt it's
become really easy with .NET 2.0 so forgive me if this approach has been
deprecated ;).

Show quoteHide quote

"SatCom" <Sat***@discussions.microsoft.com> wrote in message
news:34ECC198-6A40-42BE-8CFE-068565BFBDBC@microsoft.com...
> Hello,
> I had originally posted this in the winforms.controls discussion, forgive
> the double post, Here is where I need help...
>
> I have been porting some VB6 to VB2005 and here is the issue with the
> serial
> port.
> I am looking to update controls on the main form (textbox, listbox, etc)
> when a call comes in. I can retrieve the ring status, caller-id etc, but
> when I go to update a textbox, I receive a threading exception issue. As I
> understand it, the "datareceived" event is raised on a second thread so I
> can
> not directly update controls on the main form or (first thread) without
> using
> INVOKE. My question is How do I do that?
>
> Private Sub m_CommPort_DataReceived(ByVal sender As Object, _
>          ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles
> m_CommPort.DataReceived
>        Dim strModemRecBuffer As String = ""
>        strModemRecBuffer = m_CommPort.ReadExisting
> ...
> ...Extract the data from the string
> ...
> ...I realize this next line is the (Thread exception) since the control is
> on the main form.
> txtIncomingCall.text = strModemRecBuffer(index)
>
> So how do I use invoke to update the controls on the first thread?
> Any help would be appreciated Thanks,
>
> SatCom

8 May 2006 5:39 PM

Dick Grier

Hi,

See my reply in the framework newsgroup. I have a VB .NET example on my
website that you can download that shows how to do this.

Dick

--
Richard Grier, MVP
Hard & Software
Author of Visual Basic Programmer's Guide to Serial Communications, Fourth
Edition,
ISBN 1-890422-28-2 (391 pages, includes CD-ROM). July 2004, Revised March
2006.
See www.hardandsoftware.net for details and contact information.

9 May 2006 5:23 AM

SatCom

Thanks to you guys. I appreciate the help.