'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.ComponentModel.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.ComponentModel.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.ComponentModel.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.CompilerServices.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.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.btnStartProcess = New System.Windows.Forms.Button
Me.btnCancel = New System.Windows.Forms.Button
Me.prgLongProcess = New System.Windows.Forms.ProgressBar
Me.bgrLongProcess = New System.ComponentModel.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.ComponentModel.BackgroundWorker
End Class
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