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