如何刷新backgroundworker - VB.NET

问题描述

我想在点击按钮时刷新后台工作人员进行刷新。这是为了在刷新后刷新标签。但是，当我这样做时，我收到错误后台工作人员很忙。所以我只希望背景工作者等到忙碌结束再次运行它。请帮助。



我尝试过：

I want to refresh the backgroundworker to refresh when I click on a button. This is for the label to refresh just after the refresh. However, when I do that, I am getting error Background worker is busy. So I want only the backgroundworker to wait until the busy is over and run it again. Kindly help.

What I have tried:

Private Sub BackgroundWorker1_DoWork(sender As Object, e As DoWorkEventArgs) Handles BackgroundWorker1.DoWork
        BackgroundWorker1.WorkerSupportsCancellation = True


        Try
            Dim ur As New Uri("http://www.find-ip-address.org/")
            Dim req As HttpWebRequest = HttpWebRequest.Create(ur)
            Dim res As HttpWebResponse = req.GetResponse()
            If (res.StatusCode = HttpStatusCode.OK) Then
                Dim receiveStream As Stream = res.GetResponseStream()
                Dim readStream As StreamReader = Nothing
                If (res.CharacterSet = Nothing) Then
                    readStream = New StreamReader(receiveStream)
                Else
                    readStream = New StreamReader(receiveStream, Encoding.GetEncoding(res.CharacterSet))
                    Dim data As String = readStream.ReadToEnd()
                    res.Close()
                    readStream.Close()
                    Dim left = "My IP Country Name:"
                    Dim right = "IP Address Lookup Location"
                    Dim indexLeft As Integer = data.IndexOf(left)
                    Dim indexRight As Integer = data.IndexOf(right)
                    lookupData = data.Substring(indexLeft + left.Length, indexRight - indexLeft - left.Length)
                    flagLocation = extractSubject("</font>  <img src='", "'><br>My IP Country Continent<")
                End If
            End If
        Catch
        End Try
    End Sub
    Private Function extractSubject(ByVal left As String, ByVal right As String)
        Try
            Dim indexLeft As Integer = lookupData.IndexOf(left)
            Dim indexRight As Integer = lookupData.IndexOf(right)
            Return lookupData.Substring(indexLeft + left.Length, indexRight - indexLeft - left.Length)
        Catch
            Return "Not Resolved!"
        End Try
    End Function
#Region "informations"
    Private Function publicIP() As String
        Return extractSubject(">My IP Address lookup for ", " show IP which")
    End Function
#End Region
    Public Sub BackgroundWorker1_RunWorkerCompleted(ByVal sender As System.Object, ByVal e As System.ComponentModel.RunWorkerCompletedEventArgs) Handles BackgroundWorker1.RunWorkerCompleted
        tbPublicIP.Text = publicIP()
        BackgroundWorker1.CancelAsync()
    End Sub

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