vb.net 写入文件同步锁

  <SoapHeader("oHeader")> _
     <WebMethod()> _
     <ScriptMethod(ResponseFormat:=ResponseFormat.Json)> _
     Public Function Test_SyncLock() As String
         Dim threads() As Threading.Thread
         For i As Integer =  To
             threads(i) = New Threading.Thread(AddressOf PrintNumbers)
             threads(i).Name = String.Format("Worker thread #{0}", i)
         Next
         ' Now start each one.
         For Each t As Threading.Thread In threads
             t.Start()
         Next
         Return ""
     End Function

     Private Sub PrintNumbers()
         writeLog("", "a", Threading.Thread.CurrentThread.Name)
     End Sub

 #Region "Write Log File"

     Private threadLock As Object = New Object()
     Public Sub writeLog(ByVal dir As String, ByVal fileName As String, ByVal log As String)

         Dim filePath As String = System.IO.Path.Combine(System.Web.Hosting.HostingEnvironment.MapPath("~/"),
                                                        "Log/" & dir & "/" & fileName & ".log")
         SyncLock threadLock
             '创建目录
             Dim dirPath As String = filePath.Substring(, filePath.LastIndexOf("/"))
             If (Directory.Exists(dirPath) = False) Then
                 Directory.CreateDirectory(dirPath)
             End If
             Dim aa As System.IO.StreamWriter = New System.IO.StreamWriter(filePath, True, System.Text.Encoding.UTF8)
             aa.WriteLine(log)
             aa.Close()
             aa.Dispose()
         End SyncLock
     End Sub
 #End Region