在 C# 中检测 USB 设备的插入和移除

Question

我尝试了此线程Detecting USB drive insertion and removal using windows service and c# 中的一种解决方案。但由于对 Windows 窗体控件的线程不安全调用，我仍然遇到错误。

这是我的代码

private void initWatchers()
{

    WqlEventQuery insertQuery = new WqlEventQuery("SELECT * FROM __InstanceCreationEvent WITHIN 2 WHERE TargetInstance ISA 'Win32_USBHub'");

    ManagementEventWatcher insertWatcher = new ManagementEventWatcher(insertQuery);
    insertWatcher.EventArrived += new EventArrivedEventHandler(DeviceInsertedEvent);
    insertWatcher.Start();

    WqlEventQuery removeQuery = new WqlEventQuery("SELECT * FROM __InstanceDeletionEvent WITHIN 2 WHERE TargetInstance ISA 'Win32_USBHub'");
    ManagementEventWatcher removeWatcher = new ManagementEventWatcher(removeQuery);
    removeWatcher.EventArrived += new EventArrivedEventHandler(DeviceRemovedEvent);
    removeWatcher.Start();

}

在事件处理程序中我启动了后台工作程序

private void DeviceInsertedEvent(object sender, EventArrivedEventArgs e)
{ 
  this.backgroundWorker1.RunWorkerAsync();
}
void DeviceRemovedEvent(object sender, EventArrivedEventArgs e)
{
 this.backgroundWorker1.RunWorkerAsync();
}

backgroundworker 完成后，我确实可以访问 windows 窗体中的控件

private void backgroundWorker1_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
// access some controls of my windows form
}

所以现在我仍然会因为控件的不安全调用而出错。知道为什么吗？

Answer 1

这是因为 GUI 元素位于应用程序的 GUI 线程中，而您正试图从 BackGroundWorker 线程访问它们。您必须使用委托来处理 BackgroundWorker 中的 GUI 元素。例如：

    GUIobject.Dispatcher.BeginInvoke(
        (Action)(() => { string value = myTextBox.Text; }));

在 RunWorkerCompleted 上，您仍在尝试从 BackGroundWorker 访问 GUI 元素。