监视文件变化的类

using System;
using System.Collections.Generic;
using System.IO;
using System.ComponentModel;

namespaceFramework.Common
{
/// <summary>
/// 监视文件变化的类，包括创建、修改、删除等操作的辅助类
/// <code>
///             MyFileSystemWatcher fsw = new MyFileSystemWatcher(@"C:\Test", "Test.txt");
///             fsw.Created += new System.IO.FileSystemEventHandler(fsw_Created);
///             fsw.Changed += new System.IO.FileSystemEventHandler(fsw_Changed);
///             fsw.Deleted += new System.IO.FileSystemEventHandler(fsw_Deleted);
///             fsw.Renamed += new System.IO.RenamedEventHandler(fsw_Renamed);
///             fsw.EnableRaisingEvents = true;
/// </code>
/// </summary>
publicclass MyFileSystemWatcher : FileSystemWatcher, IDisposable
{
#region Private Members
// This Dictionary keeps the track of when an event occured last for a particular file
privateDictionary<string, datetime=""> _lastFileEvent;
// Interval in Millisecond
privateint _interval;
//Timespan created when interval is set
privateTimeSpan _recentTimeSpan;
#endregion

#region Constructors
/// <summary>
/// 构造函数，调用基类构造函数并初始化成员
/// </summary>
publicMyFileSystemWatcher() : base()
{
InitializeMembers();
}

/// <summary>
/// 指定路径进行构造
/// </summary>
/// <param name="Path">文件路径
publicMyFileSystemWatcher(stringPath) : base(Path)
{
InitializeMembers();
}

/// <summary>
/// 指定路径和过滤器进行构造
/// </summary>
/// <param name="Path">文件或文件夹路径
/// <param name="Filter">过滤器
publicMyFileSystemWatcher(stringPath, stringFilter) : base(Path, Filter)
{
InitializeMembers();
}
#endregion

#region Events
// These events hide the events from the base class.
// We want to raise these events appropriately and we do not want the
// users of this class subscribing to these events of the base class accidentally

/// <summary>
/// 文件系统发生变化
/// </summary>
publicnew eventFileSystemEventHandler Changed;
/// <summary>
/// 文件创建事件
/// </summary>
publicnew eventFileSystemEventHandler Created;
/// <summary>
/// 文件删除事件
/// </summary>
publicnew eventFileSystemEventHandler Deleted;
/// <summary>
/// 文件重命名事件
/// </summary>
publicnew eventRenamedEventHandler Renamed;
#endregion

#region Protected Methods
/// <summary>
/// 文件发生变化
/// </summary>
protectednew virtualvoid OnChanged(FileSystemEventArgs e)
{
if(Changed != null) Changed(this, e);
}
/// <summary>
/// 文件创建后
/// </summary>
protectednew virtualvoid OnCreated(FileSystemEventArgs e)
{
if(Created != null) Created(this, e);
}
/// <summary>
/// 文件删除后
/// </summary>
protectednew virtualvoid OnDeleted(FileSystemEventArgs e)
{
if(Deleted != null) Deleted(this, e);
}

/// <summary>
/// 文件重命名后
/// </summary>
protectednew virtualvoid OnRenamed(RenamedEventArgs e)
{
if(Renamed != null) Renamed(this, e);
}
#endregion

#region Private Methods

/// <summary>
/// This Method Initializes the private members.
/// Interval is set to its default value of 100 millisecond
/// FilterRecentEvents is set to true, _lastFileEvent dictionary is initialized
/// We subscribe to the base class events.
/// </summary>
privatevoid InitializeMembers()
{
Interval = 100;
FilterRecentEvents =true;
_lastFileEvent =new Dictionary<string, datetime="">();

base.Created +=new FileSystemEventHandler(OnCreated);
base.Changed +=new FileSystemEventHandler(OnChanged);
base.Deleted +=new FileSystemEventHandler(OnDeleted);
base.Renamed +=new RenamedEventHandler(OnRenamed);
}

/// <summary>
/// This method searches the dictionary to find out when the last event occured
/// for a particular file. If that event occured within the specified timespan
/// it returns true, else false
/// </summary>
/// <param name="FileName">The filename to be checked
/// <returns>True if an event has occured within the specified interval, False otherwise</returns>
privatebool HasAnotherFileEventOccuredRecently(stringFileName)
{
boolretVal = false;

// Check dictionary only if user wants to filter recent events otherwise return Value stays False
if(FilterRecentEvents)
{
if(_lastFileEvent.ContainsKey(FileName))
{
// If dictionary contains the filename, check how much time has elapsed
// since the last event occured. If the timespan is less that the
// specified interval, set return value to true
// and store current datetime in dictionary for this file
DateTime lastEventTime = _lastFileEvent[FileName];
DateTime currentTime = DateTime.Now;
TimeSpan timeSinceLastEvent = currentTime - lastEventTime;
retVal = timeSinceLastEvent < _recentTimeSpan;
_lastFileEvent[FileName] = currentTime;
}
else
{
// If dictionary does not contain the filename,
// no event has occured in past for this file, so set return value to false
// and annd filename alongwith current datetime to the dictionary
_lastFileEvent.Add(FileName, DateTime.Now);
retVal =false;
}
}

returnretVal;
}

#region FileSystemWatcher EventHandlers
// Base class Event Handlers. Check if an event has occured recently and call method
// to raise appropriate event only if no recent event is detected
privatevoid OnChanged(objectsender, FileSystemEventArgs e)
{
if(!HasAnotherFileEventOccuredRecently(e.FullPath))
this.OnChanged(e);
}

privatevoid OnCreated(objectsender, FileSystemEventArgs e)
{
if(!HasAnotherFileEventOccuredRecently(e.FullPath))
this.OnCreated(e);
}

privatevoid OnDeleted(objectsender, FileSystemEventArgs e)
{
if(!HasAnotherFileEventOccuredRecently(e.FullPath))
this.OnDeleted(e);
}

privatevoid OnRenamed(objectsender, RenamedEventArgs e)
{
if(!HasAnotherFileEventOccuredRecently(e.OldFullPath))
this.OnRenamed(e);
}
#endregion
#endregion

#region Public Properties

/// <summary>
/// 时间间隔，以毫秒为单位，在其中的事件被认为是“最近”
/// </summary>
publicint Interval
{
get
{
return_interval;
}
set
{
_interval = value;
// Set timespan based on the value passed
_recentTimeSpan =new TimeSpan(0, 0, 0, 0, value);
}
}

/// <summary>
/// 允许用户设置是否过滤最近发生的事件。如果此设为false，该类的行为就像System.IO.FileSystemWatcher类
/// </summary>
publicbool FilterRecentEvents {get; set; }
#endregion

#region IDisposable Members

/// <summary>
/// 释放资源

4000
/// </summary>
publicnew void Dispose()
{
base.Dispose();
}

#endregion
}
}