Visual Basic

Private Sub ButtonSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ButtonSave.Click

    Dim theMenu As New ContextMenuStrip

    theMenu.Items.Add("Export to XML", MenuExportXML.Image, AddressOf MenuExportXML_Click)
    theMenu.Items.Add("Export to CSV", MenuExportCSV.Image, AddressOf MenuExportCSV_Click)

    Dim p As New Point
    p.X = ButtonSave.Width
    p.Y = ButtonSave.Top

    theMenu.Show(ButtonSave, p)

End Sub

Private Sub doSomething()

        Dim xlApp As Microsoft.Office.Interop.Excel.Application = New Microsoft.Office.Interop.Excel.Application()
        Dim xlWk As Microsoft.Office.Interop.Excel.Workbook = xlApp.Workbooks.Add()
        Dim xlSheet As Microsoft.Office.Interop.Excel.Worksheet = xlWk.Worksheets(1)
        xlApp.Visible = True

        xlSheet.Range("A1").Value = "Some Text Value on 1 line"

        xlSheet.Range("A5").Value = "Some text value on" + vbCrLf + "2 lines"

        xlSheet.Columns().AutoFit()
        xlSheet.Rows().AutoFit()

    End Sub

 Public Class Form1
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim BG As New System.ComponentModel.BackgroundWorker
     'Every time you click button1, BG creates a new Instance of BackgroundWorker in separate thread
        'So it is not Necessary to check whether it is busy or not.
        BG.WorkerReportsProgress = True 'Enable reporting

        AddHandler BG.DoWork, AddressOf BackgroundWorker_DoWork '
        AddHandler BG.RunWorkerCompleted, AddressOf BackgroundWorker_RunWorkerCompleted
        AddHandler BG.ProgressChanged, AddressOf BackgroundWorker_ProgressChanged

        Static Cnt As Integer = 1 'Number of threads
        BG.RunWorkerAsync(Cnt)
        Cnt = Cnt + 1
    End Sub

    Private Sub BackgroundWorker_DoWork(ByVal sender As System.Object, ByVal e As System.ComponentModel.DoWorkEventArgs)
        Dim stp As New Stopwatch 'Only for test purpose
        stp.Start()
        Do 'this loop never ends
            If stp.ElapsedMilliseconds Mod 1000 = 0 Then
                CType(sender, System.ComponentModel.BackgroundWorker).ReportProgress(stp.ElapsedMilliseconds, e.Argument)
                Threading.Thread.Sleep(100)
            End If
            'Perform your huge task here. I did it an infinite Do Loop. No problem to do this. What is yours?
        Loop
    End Sub

    Private Sub BackgroundWorker_ProgressChanged(ByVal sender As Object, ByVal e As System.ComponentModel.ProgressChangedEventArgs)
        TextBox1.AppendText(e.UserState.ToString & "->" & e.ProgressPercentage & ", ")
    End Sub

    Private Sub BackgroundWorker_RunWorkerCompleted(ByVal sender As Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs)
        'Never used  to call BackgroundWorker.RunWorkerAsync. what is your problem?
        'I never intended to use this to call BackgroundWorker.RunWorkerAsync for second time.
    End Sub
End Class