VB.Net Tutorial/GUI/BackgroundWorker
Background worker
<source lang="vbnet">Imports System.Windows.Forms
public class BackgroundWorker
public Shared Sub Main Application.Run(New Form1) End Sub
End class Public Class Form1
" Display the current time. Private Sub tmrUpdateClock_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tmrUpdateClock.Tick lblTime.Text = Now.ToString("T") End Sub " Start the asynchronous calculation. Private Sub btnGo_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGo.Click btnGo.Enabled = False lblWorking.Text = "Working..." Me.Cursor = Cursors.WaitCursor Application.DoEvents() bgwLongCalculation.RunWorkerAsync(5) End Sub Private Sub bgwLongCalculation_DoWork(ByVal sender As Object, ByVal e As System.ruponentModel.DoWorkEventArgs) Handles bgwLongCalculation.DoWork For i As Integer = 0 To 100000 For j As Integer = 0 To 100000 For k As Integer = 0 To 100000 Next k Next j Next i End Sub " The long task is done. Private Sub bgwLongCalculation_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ruponentModel.RunWorkerCompletedEventArgs) Handles bgwLongCalculation.RunWorkerCompleted btnGo.Enabled = True lblWorking.Text = "Done..." Me.Cursor = Cursors.Default End Sub
End Class <Global.Microsoft.VisualBasic.rupilerServices.DesignerGenerated()> _ Partial Public Class Form1
Inherits System.Windows.Forms.Form "Form overrides dispose to clean up the component list. <System.Diagnostics.DebuggerNonUserCode()> _ Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean) If disposing AndAlso components IsNot Nothing Then components.Dispose() End If MyBase.Dispose(disposing) End Sub "Required by the Windows Form Designer Private components As System.ruponentModel.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.ruponents = New System.ruponentModel.Container Me.btnGo = New System.Windows.Forms.Button Me.lblTime = New System.Windows.Forms.Label Me.tmrUpdateClock = New System.Windows.Forms.Timer(Me.ruponents) Me.bgwLongCalculation = New System.ruponentModel.BackgroundWorker Me.lblWorking = New System.Windows.Forms.Label Me.SuspendLayout() " "btnGo " Me.btnGo.Location = New System.Drawing.Point(8, 8) Me.btnGo.Name = "btnGo" Me.btnGo.Size = New System.Drawing.Size(48, 23) Me.btnGo.TabIndex = 0 Me.btnGo.Text = "Go" " "lblTime " Me.lblTime.AutoSize = True Me.lblTime.Location = New System.Drawing.Point(232, 8) Me.lblTime.Name = "lblTime" Me.lblTime.Size = New System.Drawing.Size(36, 13) Me.lblTime.TabIndex = 1 Me.lblTime.Text = "lblTime" " "tmrUpdateClock " Me.tmrUpdateClock.Enabled = True Me.tmrUpdateClock.Interval = 250 " "bgwLongCalculation " " "lblWorking " Me.lblWorking.Location = New System.Drawing.Point(80, 8) Me.lblWorking.Name = "lblWorking" Me.lblWorking.Size = New System.Drawing.Size(112, 24) Me.lblWorking.TabIndex = 2 Me.lblWorking.TextAlign = System.Drawing.ContentAlignment.MiddleLeft " "Form1 " Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!) Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font Me.ClientSize = New System.Drawing.Size(292, 80) Me.Controls.Add(Me.lblWorking) Me.Controls.Add(Me.lblTime) Me.Controls.Add(Me.btnGo) Me.Name = "Form1" Me.Text = "UseBackgroundWorker" Me.ResumeLayout(False) Me.PerformLayout() End Sub Friend WithEvents btnGo As System.Windows.Forms.Button Friend WithEvents lblTime As System.Windows.Forms.Label Friend WithEvents tmrUpdateClock As System.Windows.Forms.Timer Friend WithEvents bgwLongCalculation As System.ruponentModel.BackgroundWorker Friend WithEvents lblWorking As System.Windows.Forms.Label
End Class</source>
Long process and GUI
<source lang="vbnet">"Visual Basic 2005 Programmer"s Reference "by Rod Stephens (Author) "# Publisher: Wrox (October 21, 2005) "# Language: English "# ISBN-10: 0764571982 "# ISBN-13: 978-0764571985 Imports System.Windows.Forms
public class BackgroundWorkder
public Shared Sub Main Application.Run(New Form1) End Sub
End class Public Class Form1
" Start the long process. Private Sub btnStartProcess_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles btnStartProcess.Click " Get ready. btnStartProcess.Enabled = False btnCancel.Enabled = True prgLongProcess.Value = 0 " Start the worker. bgrLongProcess.WorkerReportsProgress = True bgrLongProcess.WorkerSupportsCancellation = True bgrLongProcess.RunWorkerAsync() End Sub " Cancel the long process. Private Sub btnCancel_Click(ByVal sender As System.Object, _ ByVal e As System.EventArgs) Handles btnCancel.Click bgrLongProcess.CancelAsync() End Sub " Display the progress. Private Sub bgrLongProcess_ProgressChanged(ByVal sender As Object, _ ByVal e As System.ruponentModel.ProgressChangedEventArgs) _ Handles bgrLongProcess.ProgressChanged prgLongProcess.Value = e.ProgressPercentage End Sub " The worker is done. Private Sub bgrLongProcess_RunWorkerCompleted(ByVal sender As Object, _ ByVal e As System.ruponentModel.RunWorkerCompletedEventArgs) _ Handles bgrLongProcess.RunWorkerCompleted btnStartProcess.Enabled = True btnCancel.Enabled = False End Sub " Do the work. Private Sub bgrLongProcess_DoWork(ByVal sender As Object, _ ByVal e As System.ruponentModel.DoWorkEventArgs) Handles bgrLongProcess.DoWork " This example just wastes some time. Const NUM_SECONDS As Integer = 5 For i As Integer = 1 To NUM_SECONDS " Pause 1 second. Dim wait_until As Date = Now.AddSeconds(1) Do While Now < wait_until Loop " If the user has canceled, stop. If bgrLongProcess.CancellationPending Then Exit Sub " Report our progress. bgrLongProcess.ReportProgress(CInt(100 * i / NUM_SECONDS)) Next i End Sub
End Class <Global.Microsoft.VisualBasic.rupilerServices.DesignerGenerated()> _ Partial Public Class Form1
Inherits System.Windows.Forms.Form "Form overrides dispose to clean up the component list. <System.Diagnostics.DebuggerNonUserCode()> _ Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean) If disposing AndAlso components IsNot Nothing Then components.Dispose() End If MyBase.Dispose(disposing) End Sub "Required by the Windows Form Designer Private components As System.ruponentModel.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.btnStartProcess = New System.Windows.Forms.Button Me.btnCancel = New System.Windows.Forms.Button Me.prgLongProcess = New System.Windows.Forms.ProgressBar Me.bgrLongProcess = New System.ruponentModel.BackgroundWorker Me.SuspendLayout() " "btnStartProcess " Me.btnStartProcess.Location = New System.Drawing.Point(8, 8) Me.btnStartProcess.Name = "btnStartProcess" Me.btnStartProcess.Size = New System.Drawing.Size(75, 23) Me.btnStartProcess.TabIndex = 0 Me.btnStartProcess.Text = "Start" " "btnCancel " Me.btnCancel.Location = New System.Drawing.Point(208, 8) Me.btnCancel.Name = "btnCancel" Me.btnCancel.Size = New System.Drawing.Size(72, 24) Me.btnCancel.TabIndex = 1 Me.btnCancel.Text = "Cancel" " "prgLongProcess " Me.prgLongProcess.BackColor = System.Drawing.Color.Black Me.prgLongProcess.ForeColor = System.Drawing.Color.Red Me.prgLongProcess.Location = New System.Drawing.Point(8, 48) Me.prgLongProcess.Name = "prgLongProcess" Me.prgLongProcess.Size = New System.Drawing.Size(272, 16) Me.prgLongProcess.TabIndex = 2 " "Form1 " Me.AutoScaleDimensions = New System.Drawing.SizeF(6.0!, 13.0!) Me.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font Me.ClientSize = New System.Drawing.Size(288, 75) Me.Controls.Add(Me.prgLongProcess) Me.Controls.Add(Me.btnCancel) Me.Controls.Add(Me.btnStartProcess) Me.Name = "Form1" Me.Text = "UseBackgroundWorker" Me.ResumeLayout(False) End Sub Friend WithEvents btnStartProcess As System.Windows.Forms.Button Friend WithEvents btnCancel As System.Windows.Forms.Button Friend WithEvents prgLongProcess As System.Windows.Forms.ProgressBar Friend WithEvents bgrLongProcess As System.ruponentModel.BackgroundWorker
End Class</source>