BackgroundWorker Control

ตัวอย่างนี้ เป็นคอนโทรลที่ใช้ในการทำงานแบบอยู่เบื้องหลัง ไม่กระทบกับการทำงานเบื้องหน้า หรือที่เรียกกันว่า Asynchronous นั่นเองครับ

    Private Sub BackgroundWorker1_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        For i As Integer = 0 To 100 Step +1
            If BackgroundWorker1.CancellationPending = True Then
                e.Cancel = True
                Exit For
            Else
                BackgroundWorker1.ReportProgress(i)
                System.Threading.Thread.Sleep(100)
            End If
        Next
    End Sub

    Private Sub BackgroundWorker1_ProgressChanged(sender As Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles BackgroundWorker1.ProgressChanged
        ProcessBar.Value = e.ProgressPercentage
        lbl_percent.Text = e.ProgressPercentage & "%"
    End Sub

    Private Sub BackgroundWorker1_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
        If e.Cancelled Then
            MsgBox("Cancelled")
        ElseIf e.Error IsNot Nothing Then
            MessageBox.Show(e.Error.Message)
        Else
            MsgBox("Completed")
        End If

        BackgroundWorker1.Dispose()
    End Sub

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        BackgroundWorker1.WorkerReportsProgress = True
        BackgroundWorker1.WorkerSupportsCancellation = True
        ProcessBar.Maximum = 100
    End Sub

    Private Sub btn_Cancel_Click(sender As Object, e As EventArgs) Handles btn_Cancel.Click
        BackgroundWorker1.CancelAsync()
    End Sub

    Private Sub btn_Progress_Click(sender As Object, e As EventArgs) Handles btn_Progress.Click
        BackgroundWorker1.RunWorkerAsync()
    End Sub