Question

我正在开发一些代码来检测目录中的新文件，并通过FileSystemWatcher的Created事件在新线程中发出信号。在测试时我发现在从事件中删除了事件处理程序后，正在使用的线程没有关闭。这是为什么？当我删除事件处理程序时，我做错了吗？

我的代码如下所示：

Private fileSystemWatcher As FileSystemWatcher
Private fileSystemEventHandler As New FileSystemEventHandler(AddressOf UpdateSomething)
Private isStopping As Boolean

Private Sub NewThread()
    fileSystemWatcher = New FileSystemWatcher("C:\Temp")
    fileSystemWatcher.Filter = "*.xml"
    fileSystemWatcher.IncludeSubdirectories = False
    fileSystemWatcher.NotifyFilter = NotifyFilters.FileName
    AddHandler fileSystemWatcher.Created, fileSystemEventHandler
    fileSystemWatcher.EnableRaisingEvents = True
End Sub

Private Sub UpdateSomething(ByVal source As Object, ByVal e As FileSystemEventArgs)
    Thread.CurrentThread.Name = "UpdateSomething"
    Console.WriteLine(e.FullPath)
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    fileSystemWatcher.EnableRaisingEvents = False
    RemoveHandler fileSystemWatcher.Created, fileSystemEventHandler
    fileSystemWatcher.Dispose()
    fileSystemWatcher = Nothing
End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
    Dim thread As New Thread(AddressOf NewThread)
    thread.Name = "NewThread"
    thread.Start()
End Sub

所以首先我开始点击Button 2来启动事件处理程序。我将xml文件复制到Temp文件夹，该事件将触发并设置线程的名称。之后，我将单击按钮1以删除事件处理程序。如果我暂停执行，则线程“UpdateSomething”仍将存在。有人可以解释原因吗？

Answer 1

当您按下Button1时，将xml文件添加到临时文件夹时不再调用UpdateSomething。这意味着它已成功删除了事件处理程序。但是，处理程序的实例仍可以运行。删除事件处理程序仅断开函数与事件的连接。如果线程仍处于活动状态，您应该能够使用Thread.cancelJob终止它。

Answer 2

旧问题，但我想我会以任何方式结束。正如@ thomas-levesque所说，这是因为ThreadPool。

在VB.NET中删除事件处理程序时，不会删除线程

2 个答案: