wasSharpNET

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/IO/FileSystemWatcher.cs
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using System;
using System.IO;
using System.Runtime.Caching;
 
namespace wasSharpNET.IO
{
/// <summary>
/// Filesystem watcher that ensures events are not fired twice
/// </summary>
/// <remarks>derived from Ben Hall @ benhall.io</remarks>
public class FileSystemWatcher : IDisposable
{
public event FileSystemEventHandler FilesytemEvent;
private readonly CacheItemPolicy _cacheItemPolicy;
private readonly int _cacheTimeMilliseconds = 1000;
private readonly MemoryCache _memCache;
 
public FileSystemWatcher(string path, NotifyFilters notifyFilters, string filter)
{
_memCache = MemoryCache.Default;
 
var watcher = new System.IO.FileSystemWatcher
{
Path = path,
NotifyFilter = notifyFilters,
Filter = filter
};
 
_cacheItemPolicy = new CacheItemPolicy
{
RemovedCallback = OnRemovedFromCache
};
 
watcher.Changed += OnChanged;
watcher.EnableRaisingEvents = true;
}
 
public FileSystemWatcher(string path, NotifyFilters notifyFilters, string filter, int timeout) : this(path,
notifyFilters, filter)
{
_cacheTimeMilliseconds = timeout;
}
 
// Add file event to cache for CacheTimeMilliseconds
private void OnChanged(object source, FileSystemEventArgs e)
{
_cacheItemPolicy.AbsoluteExpiration =
DateTimeOffset.Now.AddMilliseconds(_cacheTimeMilliseconds);
 
// Only add if it is not there already (swallow others)
_memCache.AddOrGetExisting(e.Name, e, _cacheItemPolicy);
}
 
// Handle cache item expiring
private void OnRemovedFromCache(CacheEntryRemovedArguments args)
{
if (args.RemovedReason != CacheEntryRemovedReason.Expired) return;
 
// Now actually handle file event.
OnFileSystemEvent((FileSystemEventArgs)args.CacheItem.Value);
}
 
protected virtual void OnFileSystemEvent(FileSystemEventArgs e)
{
FilesytemEvent?.Invoke(this, e);
}
 
public void Dispose()
{
_memCache.Dispose();
}
}
}