问如何使用backgroundworker在单击按钮时显示动画加载gif vb.net

EN

    Dim strRow As String()              'String array to read all fields in a row
Dim dblAmount As Double             'Variable for total amount 
Dim blnReported As Boolean = True   'Flag to check progress report completed or not

'Create TextFieldParser class to parse the stock.csv file in the current location
Dim txtFile As FileIO.TextFieldParser

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    'Allow background operation to be cancelled
    bgWorker.WorkerSupportsCancellation = True

    'Allow background operation to report progress
    bgWorker.WorkerReportsProgress = True

    'Disable Stop Button. It is enabled only after start
    'button is pressed
    btnStop.Enabled = False

    'set status message
    lblStatus.Text = "Press Start to import data from csv."

    'Add columns to the grid
    dgvCSVData.Columns.Add("colNo", "No")
    dgvCSVData.Columns("colNo").Width = 30
    dgvCSVData.Columns.Add("colDate", "Date")
    dgvCSVData.Columns("colDate").Width = 60
    dgvCSVData.Columns.Add("colItem", "Item")
    dgvCSVData.Columns("colItem").Width = 120
    dgvCSVData.Columns.Add("colQty", "Quantity")
    dgvCSVData.Columns("colQty").Width = 50
    dgvCSVData.Columns.Add("colUnit", "Unit")
    dgvCSVData.Columns("colUnit").Width = 30
    dgvCSVData.Columns.Add("colAmt", "Amt")
    dgvCSVData.Columns("colAmt").Width = 60
End Sub

Private Sub btnStart_Click(sender As Object, e As EventArgs) Handles btnStart.Click
    'Disable Start button and Enable Stop
    btnStart.Enabled = False
    btnStop.Enabled = True

    'set status message
    lblStatus.Text = "Importing data from CSV file."

    'Start time-consuming operation in background
    Call bgWorker.RunWorkerAsync()
End Sub

Private Sub btnStop_Click(sender As Object, e As EventArgs) Handles btnStop.Click
    'Enable Start button and disable Stop
    btnStart.Enabled = True
    btnStop.Enabled = False

    'Stop background operation
    bgWorker.CancelAsync()

    'set status message
    lblStatus.Text = "Import cancelled. Press Start again."
End Sub

Private Sub bgWorker_DoWork(sender As Object, e As System.ComponentModel.DoWorkEventArgs) Handles bgWorker.DoWork
    Dim intCount As Int16 = 0
    txtFile = New FileIO.TextFieldParser("stock.csv")
    'Specify structure of the file
    txtFile.TextFieldType = FileIO.FieldType.Delimited
    txtFile.SetDelimiters(",")

    'Skip header row
    txtFile.ReadFields()

    'Start reading data from file
    While Not txtFile.EndOfData

        If bgWorker.CancellationPending Then
            e.Cancel = True
            Exit Sub

        Else

            'Wait for Progress Report to finish
            While Not blnReported
                Application.DoEvents()
            End While

            'Read all field in a row into a string array
            strRow = txtFile.ReadFields()

            'Do some calculations and assign value to data grid
            dblAmount = CDbl(strRow(3)) * CDbl(strRow(4))

            'Add some sleep to simulate a long running operation
            System.Threading.Thread.Sleep(500)

            'Progress report pending
            blnReported = False

            'increment counter
            intCount += 1

            'Report the progress
            bgWorker.ReportProgress(10, intCount)

        End If

    End While
End Sub

Private Sub bgWorker_ProgressChanged(sender As Object, e As System.ComponentModel.ProgressChangedEventArgs) Handles bgWorker.ProgressChanged
    'Copy values to data grid
    dgvCSVData.Rows.Add(strRow)
    dgvCSVData.Rows(dgvCSVData.CurrentRow.Index - 1).Cells("colAmt").Value = dblAmount

    pgbCopyProgress.Value = e.UserState
    'Progress report finished
    blnReported = True
End Sub

Private Sub bgWorker_RunWorkerCompleted(sender As Object, e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles bgWorker.RunWorkerCompleted
    If e.Cancelled Or Not IsNothing(e.Error) Then
        'Clear the data grid
        dgvCSVData.Rows.Clear()
    Else
        'Progress completed
        pgbCopyProgress.Value = 100

        'Release txtfile
        txtFile.Dispose()
        btnStop.Enabled = False
        btnStart.Enabled = True

    End If
End Sub

 Public Function RESA_Checker(ByVal stores As String, ByVal bus_date As String, ByVal warehouse As String)
    dt = New DataTable
    bg.GetProcDataTable(connStr, "SALES_CHECKER.procedure_checker")
    cmd.Parameters.Add(New OracleParameter("stores", OracleDbType.Varchar2)).Value = stores
    cmd.Parameters.Add(New OracleParameter("bus_date", OracleDbType.Varchar2)).Value = bus_date
    cmd.Parameters.Add(New OracleParameter("warehouse", OracleDbType.Varchar2)).Value = warehouse
    cmd.Parameters.Add(New OracleParameter("O_OUTPUT", OracleDbType.RefCursor)).Direction = ParameterDirection.Output
    adap_or.SelectCommand = cmd
    adap_or.Fill(dt)


    Return dt
    ora_conn.Close()
End Function