VB.net中同步多线程

Question

    Using webClient = New System.Net.WebClient
        Dim owner = ""
        Try
            owner = webClient.DownloadString("http://" + CurrentBlog.Domain + "/test.php")
        Catch ex As Exception
        End Try
        appendToTextFile(CurrentBlog.Domain + checkdomainsowner(owner) + Microsoft.VisualBasic.vbNewLine, "gooddoorway.txt")
    End Using

我想使用threadpool运行它。

这样做的方法是

    Threading.ThreadPool.QueueUserWorkItem(
        Sub()
            Using webClient = New System.Net.WebClient
                Dim owner = ""
                Try
                    owner = webClient.DownloadString("http://" + CurrentBlog.Domain + "/test.php")
                Catch ex As Exception
                End Try
                appendToTextFile(CurrentBlog.Domain + checkdomainsowner(owner) + Microsoft.VisualBasic.vbNewLine, "gooddoorway.txt")
            End Using
        End Sub)

我希望appendToTextFile(CurrentBlog.Domain + checkdomainsowner(owner) + Microsoft.VisualBasic.vbNewLine, "gooddoorway.txt")与主线程同步。

这样做的简单方法是什么？我不想使用任何control.invoke，因为代码应该独立于任何控件运行。我不想使用全局变量，因为我的TA说这是件坏事。