Appending text to a richTextBox in a different thread and code file - vb.net

Question

With the intention of creating a program to interface with a serial port device, I recently started learning vb.net. To keep the structure neat the vb code has been split into two places; the first is the code behind for initialising, clicking buttons etc., whilst the second is for managing the comm port. Respectively, these are named 'MainWindow.xaml.vb' and 'ComPortManager.vb'.
In 'comPortManager.vb':
Dim RXArray(2047) As Char ' Array to hold received characters
Dim RXCnt As Integer ' Received character count
Private Sub comPort_DataReceived(ByVal sender As Object, ByVal e As SerialDataReceivedEventArgs) Handles comPort.DataReceived
Do
RXCnt = 0
Do
'Populates the array, RXArray and counts the number of characters, RXCnt
Loop Until (comPort.BytesToRead = 0) 'Keeps reading the buffer until it is empty
'Code for posting to the richTextBox
Loop Until (comPort.BytesToRead = 0) 'If the buffer has been written to in the meantime, repeat
End Sub
The 'MainWindow.xaml' contains a ribbon (Microsoft's October 2010 release) with controls for settings, opening, closing and sending (keeping it all separate and simple for now), with the rest of the window being a richTextBox entitled 'RichTextBox1'.
The search for a way to post the contents of RXArray to RichTextBox1 brought up many suggestions based around Invoke or BeginInvoke. Indeed, working examples have been run successfully but all the code associated with Invoke has been in one file, the code behind. (Correct me if I'm wrong, but this sounds fine for small programs but could get bloated with medium to larger programs, hence me wanting to find a better solution)
The code closest to running (I believe) is as follows:
'In comPort_DataReceived... after populating the array
If RichTextBox1.InvokeRequired Then
RichTextBox1.Invoke(New MethodInvoker(AddressOf Display))
End If
'and back in the main code
Public Delegate Sub MethodInvoker()
Private Sub Display()
RichTextBox1.AppendText(New String(RXArray, 0, RXCnt))
End Sub
This has a few problems and I'm not sure in what direction to go at this stage. RichTextBox1 is in a different thread hence not recognised; InvokeRequired is not a member of System.Windows.Controls.RichTextBox, likewise with Invoke; and finally, in examples, the delegate entitled MethodInvoker was never stated as above.
Any help on this topic is most appreciated. In these few weeks, Invoke, BeginInvoke etc. have somewhat eluded my comprehension. Regards, Jonathan

Answer 1

we have a large scale application which a textbox has the status of many threads appended to it concurrently, and from different forms. this is a dumbed down version of it:
Public Sub addToMessageBox(ByVal msg As String)
If Me.InvokeRequired Then
Dim d As New AddToMessageBoxDelegate(AddressOf Me.addToMessageBox)
Me.BeginInvoke(d, New Object() {msg})
Else
Try
Me.MessageBox.AppendText("--" + msg + vbCrLf)
Catch ex As Exception
End Try
End If
End Sub
The delegate is declared at the begining
Private Delegate Sub AddToMessageBoxDelegate(ByVal msg As String)
the biggest difference that I can see is that I use the parent class's beginInvoke() and InvokeRequired(). I'd say give this a try. Call the parentClass.AddToMessageBox("Text you want to append") where you are calling the display().