SerialPort and Control Updating in MDI form - vb.net

Question

As my title implies i have the following problem, i am receiving data from serial port and i update a richtextbox in a MDI Form with the control.invoke method
(Code in SerialPort.DataReceived Event)
If myTerminal.Visible Then
myTerminal.MyRichTextBox1.Invoke(New MethodInvoker(Sub()
myTerminal.MyRichTextBox1.AppendText(dataLine & vbCrLf)
End Sub))
End If
But as a mdi form it has the ability to close and reopen. So when the serialport is sending data to richtextbox and the user click the close button and the form gets disposed. Then the error "Invoke or BeginInvoke cannot be called on a control until the window handle has been created."... Any Idea????
My regards,
Ribben

Answer 1

That code is not in the SerialPort.DataReceived event it is in the event handler. (Yes, I'm nitpicking, but it points to a solution.) The best thing to do is have the form that owns myTerminal add the handler when it is created and remove the handler when it closes.

Answer 2

Thank you for your answer but unfortunately that's not the solution. First of all my SerialPort Class must inform 2 Forms (Form with richtextbox, Form with Listview) and another class which is responsible for drawing (Unmanaged Directx 9.0c about 4 Forms), so to implement right the serialport class i have made my own events. Again to the problme, it caused because the Serialport.DataReceived everytime it occurs creates a thread in the threadpool and when i dispose the form simply it's too slow to catch up with all the threads and so there is at least one thread which invokes the control which is already disposed!
As a temp solution i came up with (The Below code is in the TerminalForm Class which inherits Form):
Private VisibleBoolean As Boolean = False
Private Index As Integer = 0
Private Sub DataToAppend(ByVal _text As String)
If VisibleBoolean Then
Me.MyRichTextBox1.Invoke(New MethodInvoker(Sub()
Me.MyRichTextBox1.AppendText(_text & vbCrLf)
End Sub))
ElseIf Index = 1 Then
Index = 0
myDispose()
RemoveHandler myserialport.DataToSend2, AddressOf DataToAppend
End If
End Sub
Private Sub Me_Activated(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Activated
VisibleBoolean = True
AddHandler myserialport.DataToSend2, AddressOf DataToAppend
End Sub
Private Sub myDispose()
If Index = 0 And Not Me.IsDisposed Then
Me.Invoke(New MethodInvoker(Sub()
MyBase.Dispose(True)
End Sub))
End If
End Sub
Protected Overrides Sub Dispose(ByVal disposing As Boolean)
End Sub
Protected Overrides Sub OnFormClosing(ByVal e As System.Windows.Forms.FormClosingEventArgs)
Index = 1
VisibleBoolean = False
End Sub
I know i don't like either but at least it's working!
Anyother improvement or suggestion is more