Sharing specific examples of how C# uses the FileSystemWatcher control to implement file monitoring

This article mainly introduces the file monitoring function implemented by C# using the FileSystemWatcher control. It analyzes the functions of the C# FileSystemWatcher component and the specific usage skills for monitoring file changes in the form of examples. Friends in need can refer to the following

The example in this article describes the file monitoring function implemented by C# using the FileSystemWatcher control. Share it with everyone for your reference, as follows:

FileSystemWatcher

You can use the FileSystemWatcher component to monitor the file system and make changes to the file system reaction. By using the FileSystemWatcher component, you can quickly and easily start business processes when a specific file or directory is created, modified, or deleted.

For example, if a group of users are collaborating on a document stored in a shared directory on the server, you can use the FileSystemWatcher component to write an application to monitor changes to the shared directory. When a change is detected, the component can run a process to notify each user via email.

The component can be configured to monitor an entire directory and its contents, or a specific file or group of files in a specific directory. To monitor changes in all files, the Filter property should be set to the empty string (""); to monitor a specific file, the Filter property should be set to the file name of the file (for example, to monitor the file MyDoc. txt, set the Filter property to "MyDoc.txt"); you can also monitor changes in specific file types, for example, to monitor changes in text files, set the Filter property to "*.txt".

【Tip】Don’t ignore hidden files.

Can monitor several types of changes in directories or files. For example, you can monitor file or directory Attributes, LastWrite date and time, or Size changes. This goal can be achieved by setting the
FileSystemWatcher.NotifyFilter property to a value in NotifyFilters.

You can also monitor the renaming, deletion or creation of files or directories. For example, to monitor the renaming of a text file, set the Filter property to "*.txt", call a WaitForChanged method, and set the value of WatcherChangeTypes in the method to Renamed.

The following is an example. Create a FileSystemWatche component to monitor the directory specified at run time. The component is configured to monitor LastWrite and LastAccess time changes, as well as the creation, deletion or renaming of text files in the directory. If the file is changed, created, or deleted, the path to the file is printed to the console. When a file is renamed, both the old and new paths are printed to the console.

Example Use the FileSystemWatche component to monitor the directory specified at runtime:

using System;
using System.IO;
public class watcher 
{
  public static void Main(string[] args) 
  {
    //如果没有指定目录，则退出程序
    if(args.Length!=1) 
    {
      //显示调用程序的正确方法
      Console.WriteLine("usage:Watcher.exe(directory)");
      return;
    }
    //创建一个新的FileSystemWatcher并设置其属性
    FileSystemWatcher watcher=new FileSystemWatcher();
    watcher.Path=args[O];
    /*监视LastAcceSS和LastWrite时间的更改以及文件或目录的重命名*/
    watcher.NotifyFilter=NotifyFilters.LastAccess | NotifyFilters.LastWrite |
           NotifyFilters.FileName | NotifyFilters.DirectoryName;
    //只监视文本文件
    watcher.Filter="*.txt";
    //添加事件句柄
    //当由FileSystemWatcher所指定的路径中的文件或目录的
    //大小、系统属性、最后写时间、最后访问时间或安全权限
    //发生更改时，更改事件就会发生
    watcher.Changed +=new FileSystemEventHandler(OnChanged);
    //由FileSystemWatcher所指定的路径中文件或目录被创建时，创建事件就会发生
    watcher.Created +=new FileSystemEventHandler(OnChanged);
    //当由FileSystemWatcher所指定的路径中文件或目录被删除时，删除事件就会发生
    watcher.Deleted +=new FileSystemEventHandler(OnChanged) ;
    //当由FileSystemWatcher所指定的路径中文件或目录被重命名时，重命名事件就会发生
    watcher.Renamed +=new RenamedEventHandler(OnRenamed);
    //开始监视
    watcher.EnableRaisingEvents=true;
    //等待用户退出程序
    Console.WriteLine("Press\'q\' to quit the sample.");
    while(Console.Read()!='q');
  }
  //定义事件处理程序
  public static void OnChanged(object sender,FileSystemEventArgs e) 
  {
    //指定当文件被更改、创建或删除时要做的事
    Console.WriteLine("file:"+e.FullPath+""+e.ChangeType);
  }
  public static void OnRenamed(object sender,RenamedEventArgs e) 
  {
    //指定当文件被重命名时发生的动作
    Console.WriteLine("Fi]e:{0} renamed to{1}",e.OldFullPath,e.FullPath);
  }
}

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