从文件系统观察器事件更新列表框
本文关键字:更新 列表 事件 文件系统 观察 | 更新日期: 2023-09-27 18:34:27
我想从FileSystemWatcher
事件中更新ListBox
。当事件运行时,我收到此错误:
Unhandled Exception: System.InvalidOperationException: The calling thread cannot access this object because a different thread owns it.
at System.Windows.Threading.Dispatcher.VerifyAccess()
at System.Windows.DependencyObject.GetValue(DependencyProperty dp)
at System.Windows.Controls.Panel.get_IsItemsHost()
at System.Windows.Controls.Panel.VerifyBoundState()
at System.Windows.Controls.Panel.OnItemsChanged(Object sender, ItemsChangedEventArgs args)
at System.Windows.Controls.ItemContainerGenerator.OnItemAdded(Object item, Int32 index)
at System.Windows.Controls.ItemContainerGenerator.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
at System.Windows.Controls.ItemContainerGenerator.System.Windows.IWeakEventListener.ReceiveWeakEvent(Type managerType, Object sender, Eve
ntArgs e)
at System.Windows.WeakEventManager.DeliverEventToList(Object sender, EventArgs args, ListenerList list)
at System.Windows.WeakEventManager.DeliverEvent(Object sender, EventArgs args)
at System.Collections.Specialized.CollectionChangedEventManager.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
at System.Collections.Specialized.NotifyCollectionChangedEventHandler.Invoke(Object sender, NotifyCollectionChangedEventArgs e)
at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
at System.Windows.Controls.ItemCollection.System.Windows.IWeakEventListener.ReceiveWeakEvent(Type managerType, Object sender, EventArgs e
)
at System.Windows.WeakEventManager.DeliverEventToList(Object sender, EventArgs args, ListenerList list)
at System.Windows.WeakEventManager.DeliverEvent(Object sender, EventArgs args)
at System.Collections.Specialized.CollectionChangedEventManager.OnCollectionChanged(Object sender, NotifyCollectionChangedEventArgs args)
at System.Windows.Data.CollectionView.OnCollectionChanged(NotifyCollectionChangedEventArgs args)
at MS.Internal.Controls.InnerItemCollectionView.Add(Object item)
at System.Windows.Controls.ItemCollection.Add(Object newItem)
at DirectoryBinding.MainWindow.<.ctor>b__2(Object s, FileSystemEventArgs e) in C:'Users'dharmatech'Documents'DirectoryBinding'DirectoryBi
nding'MainWindow.xaml.cs:line 35
at System.IO.FileSystemWatcher.OnCreated(FileSystemEventArgs e)
at System.IO.FileSystemWatcher.NotifyFileSystemEventArgs(Int32 action, String name)
at System.IO.FileSystemWatcher.CompletionStatusChanged(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* overlappedPointer)
at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)
下面是演示该问题的代码:
Xaml:
<Window x:Class="DirectoryBinding.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow"
Height="350"
Width="525">
<DockPanel>
<ListBox DockPanel.Dock="Top" Name="listBox"/>
</DockPanel>
</Window>
C#
using System.Linq;
using System.Windows;
using System.IO;
namespace DirectoryBinding
{
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
new DirectoryInfo("c:/users/dharmatech").GetFileSystemInfos().ToList().ForEach(
info => listBox.Items.Add(info.FullName));
var fileSystemWatcher = new FileSystemWatcher("c:/users/dharmatech")
{ EnableRaisingEvents = true };
fileSystemWatcher.Created += (s, e) => listBox.Items.Add(e.FullPath);
}
}
}
关于如何做到这一点的任何建议?
这里的问题是FileSystemWatcher
在线程池而不是 UI 线程上引发其事件,但 UI 只能从 UI 线程进行修改。 在修改事件处理代码之前,需要将其移回 UI 线程
处理此问题的一种方法是使用SynchronizationContext
var context = SynchronizationContext.Current;
fileSystemWatcher.Created += (s, e) => {
context.Post(val => listBox.Items.Add(e.FullPath), s);
};