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POReactive Extensions vs FileSystemWatcher
 

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    <p>One of the things that has long bugged me about the FileSystemWatcher is the way it fires multiple events for a single logical change to a file. I know why it happens, but I don't want to have to care - I just want to reparse the file once, not 4-6 times in a row. Ideally, there would be an event that only fires when a given file is done changing, rather than every step along the way.</p> <p>Over the years I've come up with various solutions to this problem, of varying degrees of ugliness. I thought Reactive Extensions would be the ultimate solution, but there's something I'm not doing right, and I'm hoping someone can point out my mistake.</p> <p>I have an extension method:</p> <pre><code>public static IObservable&lt;IEvent&lt;FileSystemEventArgs&gt;&gt; GetChanged(this FileSystemWatcher that) { return Observable.FromEvent&lt;FileSystemEventArgs&gt;(that, "Changed"); } </code></pre> <p>Ultimately, I would like to get one event per filename, within a given time period - so that four events in a row with a single filename are reduced to one event, but I don't lose anything if multiple files are modified at the same time. <code>BufferWithTime</code> sounds like the ideal solution.</p> <pre><code>var bufferedChange = watcher.GetChanged() .Select(e =&gt; e.EventArgs.FullPath) .BufferWithTime(TimeSpan.FromSeconds(1)) .Where(e =&gt; e.Count &gt; 0) .Select(e =&gt; e.Distinct()); </code></pre> <p>When I subscribe to this observable, a single change to a monitored file triggers my subscription method four times in a row, which rather defeats the purpose. If I remove the <code>Distinct()</code> call, I see that each of the four calls contains two identical events - so there is some buffering going on. Increasing the TimeSpan passed to <code>BufferWithTime</code> seems to have no effect - I went as high as 20 seconds without any change in behavior.</p> <p>This is my first foray into Rx, so I'm probably missing something obvious. Am I doing it wrong? Is there a better approach? Thanks for any suggestions...</p>
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    1. USRuben Bartelink
    1. USJoel Mueller
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    1. COCould you wrap this up in a complete program? I'd be interested in investigating it...
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      1. USJon Skeet
    2. COYes, I'll make an isolated test case. Now that I think of it, I have more than one watcher handling more than one folder, and I need to prove that it isn't four different watchers receiving the same pair of events somehow anyway.
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      1. USJoel Mueller
 

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