我有一个应用程序,我正在寻找一个文本文件,如果对文件做了任何更改,我使用OnChanged事件处理程序来处理事件。我正在使用NotifyFilters。LastWriteTime,但是事件仍然被触发两次。这是代码。
public void Initialize()
{
FileSystemWatcher _fileWatcher = new FileSystemWatcher();
_fileWatcher.Path = "C:\\Folder";
_fileWatcher.NotifyFilter = NotifyFilters.LastWrite;
_fileWatcher.Filter = "Version.txt";
_fileWatcher.Changed += new FileSystemEventHandler(OnChanged);
_fileWatcher.EnableRaisingEvents = true;
}
private void OnChanged(object source, FileSystemEventArgs e)
{
.......
}
在我的情况下,OnChanged被调用两次,当我改变文本文件version.txt并保存它。
解决方案实际上取决于用例。您是否在注意不更改的新文件,或每隔一段时间更改一次的文件或经常更改的文件?在我的情况下,它的变化不太频繁,我不想错过任何这些变化。
但是我也不想在写入过程尚未完成写入的地方发生更改事件。
在我的情况下,我注意到6 (6 !!)onchange事件写一个125字符的txt文件。
我的解决方案是民意调查和改变事件的混合,民意调查经常被消极地看待。正常轮询比较慢,比如每10秒一次,以防FileSystemWatcher (FSW)“错过”一个事件。轮询立即响应FSW更改事件。
关键是在FSW。更改事件时,轮询速度加快,例如每100毫秒,并等待直到文件稳定。因此我们有了“两阶段轮询”:阶段1比较慢,但在FSW文件更改事件时立即响应。第二阶段是快速的,等待一个稳定的文件。
如果FSW检测到多个文件更改,每个事件都会加速轮询循环,并有效地启动一个新的短等待周期。只有在轮询循环检测到上次写入时文件没有进一步的变化之后,它才假定文件是稳定的,并且您的代码可以处理更改后的文件。
我选择了10秒和100毫秒的超时,但是您的用例可能需要不同的超时值。
这里是轮询,其中AppConfig。fiIO是要注意的FileInfo:
private readonly EventWaitHandle ewhTimeout = new AutoResetEvent(false);
private void TwoPhasedPolling()
{
bool WaitForChange = true; //false: wait until stable
DateTime LastWriteTime = DateTime.MinValue;
while (true)
{
// wait for next poll (timeout), or FSW event
bool GotOne = ewhTimeout.WaitOne(WaitForChange ? 10 * 1000 : 100);
if (GotOne)
{
// WaitOne interrupted: end of Phase1: FSW detected file change
WaitForChange = false;
}
else
{
// WaitOne timed out: Phase2: check file write time for change
if (AppConfig.fiIO.LastWriteTime > LastWriteTime)
{
LastWriteTime = AppConfig.fiIO.LastWriteTime;
}
else
{
// End of Phase2: file has changed and is stable
WaitForChange = true;
// action on changed file
... your code here ...
}}}}
private void fileSystemWatcher1_Changed(object sender, FileSystemEventArgs e)
{
ewhTimeout.Set();
}
NB:是的,我也不喜欢}}}},但它使列表更短,这样你就不必滚动了:-)
In my case need to get the last line of a text file that is inserted by other application, as soon as insertion is done. Here is my solution. When the first event is raised, i disable the watcher from raising others, then i call the timer TimeElapsedEvent because when my handle function OnChanged is called i need the size of the text file, but the size at that time is not the actual size, it is the size of the file imediatelly before the insertion. So i wait for a while to proceed with the right file size.
private FileSystemWatcher watcher = new FileSystemWatcher();
...
watcher.Path = "E:\\data";
watcher.NotifyFilter = NotifyFilters.LastWrite ;
watcher.Filter = "data.txt";
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.EnableRaisingEvents = true;
...
private void OnChanged(object source, FileSystemEventArgs e)
{
System.Timers.Timer t = new System.Timers.Timer();
try
{
watcher.Changed -= new FileSystemEventHandler(OnChanged);
watcher.EnableRaisingEvents = false;
t.Interval = 500;
t.Elapsed += (sender, args) => t_Elapsed(sender, e);
t.Start();
}
catch(Exception ex) {
;
}
}
private void t_Elapsed(object sender, FileSystemEventArgs e)
{
((System.Timers.Timer)sender).Stop();
//.. Do you stuff HERE ..
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.EnableRaisingEvents = true;
}
试试下面的代码:
class WatchPlotDirectory
{
bool let = false;
FileSystemWatcher watcher;
string path = "C:/Users/jamie/OneDrive/Pictures/Screenshots";
public WatchPlotDirectory()
{
watcher = new FileSystemWatcher();
watcher.Path = path;
watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite
| NotifyFilters.FileName | NotifyFilters.DirectoryName;
watcher.Filter = "*.*";
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.Renamed += new RenamedEventHandler(OnRenamed);
watcher.EnableRaisingEvents = true;
}
void OnChanged(object sender, FileSystemEventArgs e)
{
if (let==false) {
string mgs = string.Format("File {0} | {1}",
e.FullPath, e.ChangeType);
Console.WriteLine("onchange: " + mgs);
let = true;
}
else
{
let = false;
}
}
void OnRenamed(object sender, RenamedEventArgs e)
{
string log = string.Format("{0} | Renamed from {1}",
e.FullPath, e.OldName);
Console.WriteLine("onrenamed: " + log);
}
public void setPath(string path)
{
this.path = path;
}
}
代码可自定义禁用阻止第二个观察者升起的时间间隔,如果他们存在,则不阻止观察者:
namespace Watcher
{
class Static
{
public static DateTime lastDomain { get; set; }
public static string lastDomainStr { get; set; }
}
public partial class Form1 : Form
{
int minMs = 20;//time for blocking in ms
public Form1()
{
InitializeComponent();
Static.lastDomain = new DateTime(1970, 1, 1, 0, 0, 0);
Static.lastDomainStr = "";
Start();
}
private void Start()//Start watcher
{
//...
domain.Changed += new FileSystemEventHandler(Domain);
domain.EnableRaisingEvents = true;
//...you second unblocked watchers
second.Changed += new FileSystemEventHandler(Second);
second.EnableRaisingEvents = true;
}
private void Domain(object source, FileSystemEventArgs e)
{
if (now.Subtract(Static.lastDomain).TotalMilliseconds < minMs && Static.lastDomainStr == e.FullPath)return;
//...you code here
/* if you need form access
this.Invoke(new MethodInvoker(() =>{ textBox1.Text = "...";}));
*/
Static.lastDomain = DateTime.Now;
Static.lastDomainStr = e.FullPath;
}
private void Second(object source, FileSystemEventArgs e)
{
//...Second rised
}
}
}