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。
事件如果没有问,这是一个遗憾,没有现成的解决方案样本f#。
要解决这个问题,这里有我的方法,因为我可以,而且f#是一种很棒的。net语言。
使用FSharp.Control.Reactive包过滤掉重复的事件,它只是响应式扩展的f#包装器。所有这些都可以针对全框架或netstandard2.0:
let createWatcher path filter () =
new FileSystemWatcher(
Path = path,
Filter = filter,
EnableRaisingEvents = true,
SynchronizingObject = null // not needed for console applications
)
let createSources (fsWatcher: FileSystemWatcher) =
// use here needed events only.
// convert `Error` and `Renamed` events to be merded
[| fsWatcher.Changed :> IObservable<_>
fsWatcher.Deleted :> IObservable<_>
fsWatcher.Created :> IObservable<_>
//fsWatcher.Renamed |> Observable.map renamedToNeeded
//fsWatcher.Error |> Observable.map errorToNeeded
|] |> Observable.mergeArray
let handle (e: FileSystemEventArgs) =
printfn "handle %A event '%s' '%s' " e.ChangeType e.Name e.FullPath
let watch path filter throttleTime =
// disposes watcher if observer subscription is disposed
Observable.using (createWatcher path filter) createSources
// filter out multiple equal events
|> Observable.distinctUntilChanged
// filter out multiple Changed
|> Observable.throttle throttleTime
|> Observable.subscribe handle
[<EntryPoint>]
let main _args =
let path = @"C:\Temp\WatchDir"
let filter = "*.zip"
let throttleTime = TimeSpan.FromSeconds 10.
use _subscription = watch path filter throttleTime
System.Console.ReadKey() |> ignore
0 // return an integer exit code
我可以通过添加一个函数来检查缓冲区数组中的重复项来做到这一点。
然后使用计时器在数组X时间内未被修改后执行该操作:
-每次有东西写入缓冲区时重置计时器
—对tick执行动作
这还捕获了另一种复制类型。如果修改文件夹内的文件,该文件夹也会引发Change事件。
Function is_duplicate(str1 As String) As Boolean
If lb_actions_list.Items.Count = 0 Then
Return False
Else
Dim compStr As String = lb_actions_list.Items(lb_actions_list.Items.Count - 1).ToString
compStr = compStr.Substring(compStr.IndexOf("-") + 1).Trim
If compStr <> str1 AndAlso compStr.parentDir <> str1 & "\" Then
Return False
Else
Return True
End If
End If
End Function
Public Module extentions
<Extension()>
Public Function parentDir(ByVal aString As String) As String
Return aString.Substring(0, CInt(InStrRev(aString, "\", aString.Length - 1)))
End Function
End Module
我简单地添加了一个dupe检查如下:
private void OnChanged(object source, FileSystemEventArgs e)
{
string sTabName = Path.GetFileNameWithoutExtension(e.Name);
string sLastLine = ReadLastLine(e.FullPath);
if(sLastLine != _dupeCheck)
{
TabPage tp = tcLogs.TabPages[sTabName];
TextBox tbLog = (TextBox)tp.Controls[0] as TextBox;
tbLog.Invoke(new Action(() => tbLog.AppendText(sLastLine + Environment.NewLine)));
tbLog.Invoke(new Action(() => tbLog.SelectionStart = tbLog.Text.Length));
tbLog.Invoke(new Action(() => tbLog.ScrollToCaret()));
_dupeCheck = sLastLine;
}
}
public static String ReadLastLine(string path)
{
return ReadLastLine(path, Encoding.Default, "\n");
}
public static String ReadLastLine(string path, Encoding encoding, string newline)
{
int charsize = encoding.GetByteCount("\n");
byte[] buffer = encoding.GetBytes(newline);
using (FileStream stream = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
{
long endpos = stream.Length / charsize;
for (long pos = charsize; pos < endpos; pos += charsize)
{
stream.Seek(-pos, SeekOrigin.End);
stream.Read(buffer, 0, buffer.Length);
if (encoding.GetString(buffer) == newline)
{
buffer = new byte[stream.Length - stream.Position];
stream.Read(buffer, 0, buffer.Length);
return encoding.GetString(buffer);
}
}
}
return null;
}
[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern int SendMessage(IntPtr hWnd, int wMsg, IntPtr wParam, IntPtr lParam);
private const int WM_VSCROLL = 0x115;
private const int SB_BOTTOM = 7;
/// <summary>
/// Scrolls the vertical scroll bar of a multi-line text box to the bottom.
/// </summary>
/// <param name="tb">The text box to scroll</param>
public static void ScrollToBottom(TextBox tb)
{
SendMessage(tb.Handle, WM_VSCROLL, (IntPtr)SB_BOTTOM, IntPtr.Zero);
}
我认为解决这个问题的最佳方案是使用响应式扩展
当你将事件转换为可观察对象时,你可以添加Throttling(..)(最初称为Debounce(..))
这里是示例代码
var templatesWatcher = new FileSystemWatcher(settingsSnapshot.Value.TemplatesDirectory)
{
NotifyFilter = NotifyFilters.LastWrite,
IncludeSubdirectories = true
};
templatesWatcher.EnableRaisingEvents = true;
Observable.FromEventPattern<FileSystemEventHandler, FileSystemEventArgs>(
addHandler => templatesWatcher.Changed += addHandler,
removeHandler => templatesWatcher.Changed -= removeHandler)
.Throttle(TimeSpan.FromSeconds(5))
.Subscribe(args =>
{
_logger.LogInformation($"Template file {args.EventArgs.Name} has changed");
//TODO do something
});
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
}
}
}