BackgroundWorkerEx on VB.NET

frmBGWorker.Designer.vb

<Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
Partial Class frmBGWorker
    Inherits System.Windows.Forms.Form

    'Form overrides dispose to clean up the component list.
    <System.Diagnostics.DebuggerNonUserCode()> _
    Protected Overrides Sub Dispose(ByVal disposing As Boolean)
        Try
            If disposing AndAlso components IsNot Nothing Then
                components.Dispose()
            End If
        Finally
            MyBase.Dispose(disposing)
        End Try
    End Sub

    'Required by the Windows Form Designer
    Private components As System.ComponentModel.IContainer

    'NOTE: The following procedure is required by the Windows Form Designer
    'It can be modified using the Windows Form Designer.  
    'Do not modify it using the code editor.
    <System.Diagnostics.DebuggerStepThrough()> _
    Private Sub InitializeComponent()
        Me.components = New System.ComponentModel.Container
        Me.BtnStart = New System.Windows.Forms.Button
        Me.BtnStop = New System.Windows.Forms.Button
        Me.PgbDownloadPercent = New System.Windows.Forms.ProgressBar
        Me.LblDownloadPercent = New System.Windows.Forms.Label
        Me.LblDateTime = New System.Windows.Forms.Label
        Me.TmrNow = New System.Windows.Forms.Timer(Me.components)
        Me.BgwDownload = New System.ComponentModel.BackgroundWorker
        Me.SuspendLayout()
        '
        'BtnStart
        '
        Me.BtnStart.Anchor = System.Windows.Forms.AnchorStyles.Bottom
        Me.BtnStart.Location = New System.Drawing.Point(68, 66)
        Me.BtnStart.Name = "BtnStart"
        Me.BtnStart.Size = New System.Drawing.Size(75, 23)
        Me.BtnStart.TabIndex = 0
        Me.BtnStart.Text = "Start"
        Me.BtnStart.UseVisualStyleBackColor = True
        '
        'BtnStop
        '
        Me.BtnStop.Anchor = System.Windows.Forms.AnchorStyles.Bottom
        Me.BtnStop.Enabled = False
        Me.BtnStop.Location = New System.Drawing.Point(149, 66)
        Me.BtnStop.Name = "BtnStop"
        Me.BtnStop.Size = New System.Drawing.Size(75, 23)
        Me.BtnStop.TabIndex = 1
        Me.BtnStop.Text = "Stop"
        Me.BtnStop.UseVisualStyleBackColor = True
        '
        'PgbDownloadPercent
        '
        Me.PgbDownloadPercent.Anchor = CType(((System.Windows.Forms.AnchorStyles.Top Or System.Windows.Forms.AnchorStyles.Left) _
                    Or System.Windows.Forms.AnchorStyles.Right), System.Windows.Forms.AnchorStyles)
        Me.PgbDownloadPercent.Location = New System.Drawing.Point(12, 12)
        Me.PgbDownloadPercent.Name = "PgbDownloadPercent"
        Me.PgbDownloadPercent.Size = New System.Drawing.Size(268, 23)
        Me.PgbDownloadPercent.TabIndex = 2
        '
        'LblDownloadPercent
        '
        Me.LblDownloadPercent.AutoSize = True
        Me.LblDownloadPercent.Location = New System.Drawing.Point(12, 38)
        Me.LblDownloadPercent.Name = "LblDownloadPercent"
        Me.LblDownloadPercent.Size = New System.Drawing.Size(106, 13)
        Me.LblDownloadPercent.TabIndex = 3
        Me.LblDownloadPercent.Text = "LblDownloadPercent"
        '
        'LblDateTime
        '
        Me.LblDateTime.Anchor = CType((System.Windows.Forms.AnchorStyles.Bottom Or System.Windows.Forms.AnchorStyles.Left), System.Windows.Forms.AnchorStyles)
        Me.LblDateTime.AutoSize = True
        Me.LblDateTime.Location = New System.Drawing.Point(12, 92)
        Me.LblDateTime.Name = "LblDateTime"
        Me.LblDateTime.Size = New System.Drawing.Size(67, 13)
        Me.LblDateTime.TabIndex = 4
        Me.LblDateTime.Text = "LblDateTime"
        '
        'TmrNow
        '
        Me.TmrNow.Enabled = True
        '
        'BgwDownload
        '
        Me.BgwDownload.WorkerReportsProgress = True
        Me.BgwDownload.WorkerSupportsCancellation = True
        '
        'FrmBGWorkerTest
        '
        Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.None
        Me.ClientSize = New System.Drawing.Size(292, 114)
        Me.Controls.Add(Me.LblDateTime)
        Me.Controls.Add(Me.LblDownloadPercent)
        Me.Controls.Add(Me.PgbDownloadPercent)
        Me.Controls.Add(Me.BtnStop)
        Me.Controls.Add(Me.BtnStart)
        Me.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedSingle
        Me.MaximizeBox = False
        Me.Name = "FrmBGWorkerTest"
        Me.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen
        Me.Text = "BackgroundWorker Test"
        Me.ResumeLayout(False)
        Me.PerformLayout()

    End Sub
    Friend WithEvents BtnStart As System.Windows.Forms.Button
    Friend WithEvents BtnStop As System.Windows.Forms.Button
    Friend WithEvents PgbDownloadPercent As System.Windows.Forms.ProgressBar
    Friend WithEvents LblDownloadPercent As System.Windows.Forms.Label
    Friend WithEvents LblDateTime As System.Windows.Forms.Label
    Friend WithEvents TmrNow As System.Windows.Forms.Timer
    Friend WithEvents BgwDownload As System.ComponentModel.BackgroundWorker

End Class

frmBGWorker1.vb

Public Class frmBGWorker
' Synchronous version

#Region "Field"
    Private _isBusy As Boolean
#End Region

#Region "Constructor & Destructor"
    Public Sub New()
        ' This call is required by the Windows Form Designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.
        UpdateProgress(0)

        LblDateTime.Text = ""
    End Sub
#End Region

#Region "Local Function"
    Private Sub UpdateProgress(ByVal percent As Integer)
        PgbDownloadPercent.Value = percent
        LblDownloadPercent.Text = String.Format("Download {0}%", percent)
    End Sub

    Private Sub DownloadStart()
        _isBusy = True

        For i As Integer = 1 To 100
            If Not _isBusy Then Return
            Threading.Thread.Sleep(50)  ' Simulate download
            UpdateProgress(i)
        Next

        _isBusy = False
    End Sub

    Private Sub DownloadStop()
        _isBusy = False
    End Sub
#End Region

#Region "Event"
    Private Sub BtnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnStart.Click
        BtnStop.Enabled = True
        BtnStart.Enabled = False

        DownloadStart()

        BtnStart.Enabled = True
        BtnStop.Enabled = False
        MessageBox.Show("Download Complete")
    End Sub

    Private Sub BtnStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnStop.Click
        DownloadStop()

        BtnStart.Enabled = True
        BtnStop.Enabled = False
        MessageBox.Show("Download Cancel")
    End Sub

    Private Sub TmrNow_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TmrNow.Tick
        LblDateTime.Text = String.Format("{0} [Busy = {1}]", Now.ToString(), _isBusy)
    End Sub
#End Region
End Class

frmBGWorker2.vb

Public Class frmBGWorker
' Asynchronous version

#Region "Constructor & Destructor"
    Public Sub New()
        ' This call is required by the Windows Form Designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.
        UpdateProgress(0)

        LblDateTime.Text = ""
    End Sub
#End Region

#Region "Local Function"
    Private Sub UpdateProgress(ByVal percent As Integer)
        PgbDownloadPercent.Value = percent
        LblDownloadPercent.Text = String.Format("Download {0}%", percent)
    End Sub
#End Region

#Region "Event"
    Private Sub BtnStart_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnStart.Click
        BtnStop.Enabled = True
        BtnStart.Enabled = False

        ' ตัวอย่าง RunWorkerAsync แบบไม่มี Input
        BgwDownload.RunWorkerAsync()

        ' ตัวอย่าง RunWorkerAsync แบบมี Input
        'Dim intStart As Integer = 1
        'BgwDownload.RunWorkerAsync(intStart)
    End Sub

    Private Sub BtnStop_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnStop.Click
        BgwDownload.CancelAsync()
    End Sub

    Private Sub TmrNow_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TmrNow.Tick
        LblDateTime.Text = String.Format("{0} [Busy = {1}]", Now.ToString(), BgwDownload.IsBusy)
    End Sub

    Private Sub BgwDownload_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles BgwDownload.DoWork
        Dim intStart As Integer = 1
        If e.Argument IsNot Nothing Then intStart = DirectCast(e.Argument, Integer)

        For i As Integer = intStart To 100
            If BgwDownload.CancellationPending Then e.Cancel = True : Return
            Threading.Thread.Sleep(50)  ' Simulate download
            BgwDownload.ReportProgress(i)

            ' ตัวอย่างการทำให้เกิด Error เพื่อทดสอบการตรวจสอบ Error บน BackgroundWorker
            'If i = 10 Then Throw New Exception("ทดสอบ error")
        Next

        e.Result = "ทดสอบ return ข้อมูล"
    End Sub

    Private Sub BgwDownload_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs) Handles BgwDownload.ProgressChanged
        UpdateProgress(e.ProgressPercentage)
    End Sub

    Private Sub BgwDownload_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BgwDownload.RunWorkerCompleted
        BtnStart.Enabled = True
        BtnStop.Enabled = False

        Select Case True
            Case e.Cancelled
                MessageBox.Show("Download Cancel")
            Case e.Error IsNot Nothing
                MessageBox.Show("Download Error / Error Message = " & e.Error.Message)
            Case Else
                MessageBox.Show("Download Complete / Result = " & DirectCast(e.Result, String))
        End Select
    End Sub
#End Region
End Class