CODEWITHSUNDEEP
vb.netmultithreadingeventsevent-handlingbackgroundworker
Django
Django

Reputation: 381

Background Workers and Successive Events

I'm back again, with more code than last time. I may reference my previous questions here and there but this question is independent

I managed to convince my employer to drop the proprietary serial port communications library I was made to use, so now I am starting from scratch with SerialPorts and BackgroundWorkers so that I know how they work.

Here is my code:

Imports System
Imports System.IO.Ports

Public Class Form1

    'SerialPort Port and BackgroundWorker Worker declared in form

    Delegate Sub AppendText_Delegate(ByVal txtBox As TextBox, ByVal str As String)

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load

        Port.PortName = ("COM9")
        Port.BaudRate = 115200
        Port.Parity = Parity.None
        Port.StopBits = StopBits.One
        Port.Handshake = Handshake.None
        Port.ReadTimeout = 1000
        Port.WriteTimeout = 1000

        Port.Open()

        AddHandler Port.DataReceived, AddressOf DataReceived

        Worker.WorkerReportsProgress = True
        Worker.WorkerSupportsCancellation = True

    End Sub

    Private Sub btnSend_Click(sender As System.Object, e As System.EventArgs) Handles btnSend.Click
        Port.Write(txtInput.Text & vbCrLf)
    End Sub

    Private Sub DataReceived(sender As Object, e As SerialDataReceivedEventArgs)
        Worker.RunWorkerAsync()
    End Sub

    Private Sub BackgroundWorker1_DoWork(sender As System.Object, e As System.ComponentModel.DoWorkEventArgs) Handles Worker.DoWork

        If Worker.CancellationPending Then
            e.Cancel = True
        End If
        AppendText_ThreadSafe(Me.txtOutput, Port.ReadLine())

    End Sub

    Private Sub AppendText_ThreadSafe(ByVal txtBox As TextBox, ByVal str As String)
        If txtBox.InvokeRequired Then
            Dim MyDelegate As New AppendText_Delegate(AddressOf AppendText_ThreadSafe)
            Me.Invoke(MyDelegate, New Object() {txtBox, str})
        Else
            txtBox.AppendText(str)
        End If
    End Sub

End Class

At this moment I really not sure how the DataReceived event and the BackgroundWorker work together. Where should I put Worker.RunWorkerAsync() so that it calls DoWork() only when the DataReceived event is raised? Should I bind both events to the same method?

Thanks for your help, and apologies for the simplicity of this question. I've only just started with BackgroundWorkers and am still finding my footing, so to speak.

Upvotes: 0

Views: 220

Answers (1)

Mark
Mark

Reputation: 8150

The DataReceived event of the SerialPort class is raised on a background thread, so it will not block the UI thread and you therefore don't need to use a BackgroundWorker in this case. Because DataReceived is called on a background thread, you will need to use Invoke if you need to update any UI controls from that handler.

Upvotes: 2

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