Develop Reference

Proper way to Implement a FileWatcher in a multithreading program C#

I have a multi-threaded program (3-4 threads). All the threads depend on a couple of parameters which are specified in an XML file.
Since the parameters in the XML file may be changed at any time by a user therefore, the different threads need to be notified about it and need to get the updated copy of parameters.
To monitor the changes in the XML file, I am using a FileWatcher as per the MSDN documentation.
clas ReadXML
{
//parameters
private static string Param1 = "";
private static string Param2 = "";
public static void ReadXmlParameters()
{
XmlDocument xDoc = new XmlDocument();
try
{
xDoc.Load(_ParameterFileDirrectory + #"\" + _ParameterFileDirrectory);
//parameters
Param1 = (xDoc.DocumentElement.SelectSingleNode("/Parameters/SetOne/IpAddress")).InnerText;
Param2 = (xDoc.DocumentElement.SelectSingleNode("/Parameters/SetOne/Username")).InnerText;
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);
}
}
public static void CreateXMLWatcher()
{
try
{
// Create a new FileSystemWatcher and set its properties.
FileSystemWatcher watcher = new FileSystemWatcher();
watcher.Path = _ParameterFileDirrectory;
/* Watch for changes in LastAccess and LastWrite times, and
the renaming of files or directories. */
watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite
| NotifyFilters.FileName | NotifyFilters.DirectoryName;
// Only watch .xml files.
watcher.Filter = _ParameterFileFilename; // "ParameterFile.xml";
// Add event handlers.
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.Created += new FileSystemEventHandler(OnChanged);
watcher.Deleted += new FileSystemEventHandler(OnChanged);
watcher.Renamed += new RenamedEventHandler(OnRenamed);
// Begin watching.
watcher.EnableRaisingEvents = true;
}
catch(Exception ex)
{
Console.WriteLine(ex.Message);
}
}
// Define the event handlers.
private static void OnChanged(object source, FileSystemEventArgs e)
{
// Specify what is done when a file is "Changed", "Created", or "Deleted".
Console.WriteLine("File: " + e.FullPath + " " + e.ChangeType);
if (e.ChangeType.ToString() == "Changed")
{
ReadXmlParameters(); //Read the Parameters from XML again
MyThreadClass1._waitTillParametersChange.Set(); //Notifying the thread that the parameters might have chnaged
}
}
}
The above implementation is working fine for me. I have to start the FileWatcher from the Main() using the following lines:
public static void Main()
{
ReadXml.ReadXmlParameters();
ReadXml.CreateXMLWatcher();
// Start other threads now
}
and then I start my other threads.
QUESTION: Since with the above-mentioned implementation, I have got Static methods and variables in my program so, I am wondering if this is the proper (at least acceptable) implementation of a FileWatcher or should I try to get rid of these static things by implementing ReadXml as a singleton class (or providing the same object to all the thread classes).

Create multiple instances of the same FileSystemWatcher

My program needs to monitor multiple locations, but trigger the same code for each location. As a single FileSystemWatcher can't monitor multiple locations, but is it possible to create multiple instances of it and pass in a folder path for each?
I can't hard code each FileSystemWatcher as more and more locations will need to be added in time and this needs to be done by the end users, as it is highly impractical for me to have to manually hard code a new FileSystemWatcher each time. So my plan was to have the folder paths saved to a file and the program just creates a FileSystemWatcher for each path in the list. But I have no idea if this is possible in the slightest.
Going on the Factory Method Pattern suggestion here the attempt:
I get the errors: "'List' does not contain a definition for 'add'
public void StartWatchers()
{
string[] ArrayPaths = new string[2];
List<FileSystemWatcher> watchers = new List<FileSystemWatcher>();
ArrayPaths[0] = #"K:\Daily Record Checker\Test\Test1";
ArrayPaths[1] = #"K:\Daily Record Checker\Test\Test2";
int i = 0;
foreach (String String in ArrayPaths)
{
watcher.add(MyWatcherFatory(ArrayPaths[i]));
i++;
}
//Do other stuff....
//....
//Start my watchers...
foreach (FileSystemWatcher watcher in watchers)
{
Watcher.EnableRaisingEvents = true;
i++;
}
}
FileSystemWatcher MyWatcherFatory(string path)
{
FileSystemWatcher watcher = new FileSystemWatcher(path);
watcher.Changed += Watcher_Created;
watcher.Path = path;
watcher.Filter = "*.csv";
return watcher;
}
private void Watcher_Created(object sender, FileSystemEventArgs e)
{
System.Threading.Thread.Sleep(1000);
FileInfo fileInfo = new FileInfo(e.FullPath);
if (!IsFileLocked(fileInfo))
{
CheckNumberOfRecordsInFile(e.FullPath);
}
}

Use the factory method pattern.
FileSystemWatcher MyWatcherFatory(string path, object additionalParameters)
{
FileSystemWatcher watcher = new FileSystemWatcher(path);
watcher.Changed += myWatcherChangedMethod;//Attach them to the same listeners,
//Set additional parameters...
return watcher.
}
EDIT: Based on the information you further provided:
public void StartWatchers()
{
string[] ArrayPaths = new string[2];
List<FileSystemWatcher> watchers = new List<FileSystemWatcher>();
ArrayPaths[0] = #"K:\Daily Record Checker\Test\Test1";
ArrayPaths[1] = #"K:\Daily Record Checker\Test\Test2";
int i = 0;
foreach (String String in ArrayPaths)
{
watchers.Add(MyWatcherFatory(ArrayPaths[i]));
i++;
}
//Do other stuff....
//....
//Start my watchers...
foreach (FileSystemWatcher watcher in watchers )
{
watcher.EnableRaisingEvents = true;;
i++;
}
}
FileSystemWatcher MyWatcherFatory(string path)
{
FileSystemWatcher watcher = new FileSystemWatcher(path);
watcher.Changed += Watcher_Created;
watcher.Path = path;
watcher.Filter = "*.csv";
return watcher;
}
private void Watcher_Created(object sender, FileSystemEventArgs e)
{
System.Threading.Thread.Sleep(1000);
FileInfo fileInfo = new FileInfo(e.FullPath);
if (!IsFileLocked(fileInfo))
{
CheckNumberOfRecordsInFile(e.FullPath);
}
}

Delete file using file watcher not allowing me to delete second time

My task is to delete file once the processing is completed . I am using FileWatcher to complete this task. It is watching specific folder . Suppose If i copy one file and put that in filewatcher folder it is deleting. Second time when i copy the same file and paste that in the same watching folder. This time it says that Another process is using that file . and exception is throwing . I think i am missing something. Here is my code
private static void Main(string[] args)
{
var fw = new FileSystemWatcher(EmailSetting.DataFolder)
{
IncludeSubdirectories = false
,
EnableRaisingEvents = true
};
fw.Created += (sender, e) =>
{
File.Delete(e.FullPath);
};
Console.ReadLine();
}

You receive the Created event when the file was created (hence the name). But at this point in time the other process that is actually creating it, didn't finish writing content into that file. So the file might be already there, but the other is still working on it (imagine you would copy a 8 GB file).
It would be wiser to simply write the path of the file into a list within the event and let another thread regularly check this concurrent bag (e.g. once a second). First it checks if the file exists and if yes, try to delete it. If succeeded, remove it from the bag, otherwise try again next time.
Code example
private static readonly ConcurrentQueue<FileInfo> _FileCandidates = new ConcurrentQueue<FileInfo>();
private static void Main(string[] args)
{
var watcher = new FileSystemWatcher
{
Path = #"R:\TestFolder",
IncludeSubdirectories = false,
Filter = "*.*",
};
Console.WriteLine("Start watching folder... " + watcher.Path);
watcher.Created += OnFileCreated;
watcher.EnableRaisingEvents = true;
var timer = new Timer
{
AutoReset = true,
Interval = 1000,
};
timer.Elapsed += OnTimerElapsed;
timer.Enabled = true;
Console.ReadKey();
}
static void OnTimerElapsed(object sender, ElapsedEventArgs e)
{
FileInfo file;
var stillInUseFiles = new List<FileInfo>();
Console.WriteLine("Check for file candidates...");
while (_FileCandidates.TryDequeue(out file))
{
try
{
Console.WriteLine("Delete " + file.FullName);
if (file.Exists)
file.Delete();
}
catch (IOException)
{
Console.WriteLine("Could not delete file, try again next time.");
stillInUseFiles.Add(file);
}
}
foreach (var unhappyFile in stillInUseFiles)
{
_FileCandidates.Enqueue(unhappyFile);
}
}
static void OnFileCreated(object sender, FileSystemEventArgs e)
{
Console.WriteLine("Found new file candidate " + e.FullPath);
_FileCandidates.Enqueue(new FileInfo(e.FullPath));
}

C# FileSystemWatcher Copy folder complete

I am using FileSystemWatcher to monitor a folder that will be used to do some file renaming.
The only thing that will be copied will be folders containing files. There will not be single files put into the monitored folder. This is the code for setting up the FileSystemWatcher
watcher.Path = path;
watcher.NotifyFilter = NotifyFilters.DirectoryName | NotifyFilters.FileName;
watcher.IncludeSubdirectories = true;
watcher.Filter = "*.*";
watcher.Created += new FileSystemEventHandler(watcher_Created);
watcher.Changed += new FileSystemEventHandler(watcher_Changed);
watcher.Renamed += new RenamedEventHandler(watcher_Renamed);
watcher.EnableRaisingEvents = true;
There doesn't seem to be any issues with this setup..
The folders being copied can be between 50-200mb big. Is there a way to check/make sure that all the files have completed copying before starting the renaming process.
I tried this thinking that i would get an IOException if the copying was still happening when the GetFiles() was called.
bool finishedCopying = false;
while (!finishedCopying)
{
try
{
List<FileInfo> fileList = directoryInfo.GetFiles().ToList();
AlbumSearch newAlbum = new AlbumSearch(directoryInfo);
return newAlbum;
}
catch (IOException)
{
finishedCopying = false;
}
}
If anymore information is required, just ask an i can provide.
Ta.

I gave this a go using a timer. It may not be the prettiest solution out there but at first testing it seems to be working so far. Essentially what this does is when a folder is copied to the monitored folder it will add the folder path to the AlbumList. The files in that folder will trigger the Created event. This waits for the file to finish copying. Once finished it starts a timer. If a new Created event gets triggered the timer will reset itself.
When the timer.elapsed event is triggered it assumes (and I know assumption is the mother of all f*&k ups) that there are no more files to be copied and can start to process the fully copied folder..
System.Timers.Timer eventTimer = new System.Timers.Timer();
List<string> AlbumList = new List<string>();
private void watcher_Created(object sender, FileSystemEventArgs e)
{
if (Directory.Exists(e.FullPath))
{
AlbumList.Add(e.FullPath);
}
if (File.Exists(e.FullPath))
{
eventTimer.Stop();
FileInfo newTrack = new FileInfo(e.FullPath);
while (IsFileLocked(newTrack))
{
// File is locked. Do Nothing..
}
eventTimer.Start();
}
}
private void eventTimer_Elapsed(object sender, ElapsedEventArgs e)
{
List<string> ItemToRemove = new List<string>();
foreach (var item in AlbumList)
{
DirectoryInfo di = new DirectoryInfo(item);
AlbumSearch newAlbum = new AlbumSearch(di);
if (DoSomethingMethod(newAlbum))
{
ItemToRemove.Add(item);
}
else
{
// why did it fail
}
}
foreach (var path in ItemToRemove)
{
AlbumList.Remove(path);
}
}
private bool DoSomethingMethod(AlbumSearch as)
{
// Do stuff here
return true;
}

This is a small demo app that check files at the beginning, and then uses two hashsets to track copied files. This will only work if the source directory is known. There is no way to know if a file was created from a file copy or from a direct creation, so you can only compare two known directories with Directory.GetFiles. And, as already said in comments, you will still have to check if during the copy process, other files were added / removed / renamed in the old directory
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ConsoleApplication1
{
class Program
{
static HashSet<string> oldDirFiles = new HashSet<string>();
static HashSet<string> newDirFiles = new HashSet<string>();
static string oldDir = "C:\\New Folder";
static string newDir = "C:\\New Folder 2";
static System.Threading.ManualResetEvent resetEvent = new System.Threading.ManualResetEvent(false);
static void Main(string[] args)
{
System.IO.FileSystemWatcher watcher = new System.IO.FileSystemWatcher();
watcher.Path = newDir;
watcher.NotifyFilter = NotifyFilters.DirectoryName | NotifyFilters.FileName;
watcher.IncludeSubdirectories = true;
watcher.Filter = "*.*";
watcher.Created += watcher_Created;
watcher.Changed += watcher_Changed;
watcher.Renamed += watcher_Renamed;
watcher.EnableRaisingEvents = true;
//get all files in old directory
var oldFiles = Directory.GetFiles(oldDir, "*.*", SearchOption.AllDirectories);
foreach (var file in oldFiles)
oldDirFiles.Add(file);
resetEvent.WaitOne();
//now launch the directory copy
//then you have to check if in the meaning time, new files were added or renamed
//that could be done also with a watcher in the old directory
}
static void watcher_Renamed(object sender, RenamedEventArgs e)
{
throw new NotImplementedException();
}
static void watcher_Changed(object sender, FileSystemEventArgs e)
{
throw new NotImplementedException();
}
static void watcher_Created(object sender, FileSystemEventArgs e)
{
//check if the copied file was in the old directory before starting
if (oldDirFiles.Contains(e.FullPath.Replace(newDir, oldDir)))
{
newDirFiles.Add(e.FullPath);
//if all the files have been copied, the file count will be the same in the two hashsets
//the resetevent.Set() signal the waiting thread and the program can proceed
if (newDirFiles.Count == oldDirFiles.Count)
resetEvent.Set();
}
}
}
}

Filesystemwatcher double entries

I made a small winforms application to monitor a certain folder for new pdf files, if a new pdf file is created in the particulair folder it will copy it to an other location.
The problem i'm having is that the filesystemwatcher creates double/multiple entries in my listbox, how can i solve this?
namespace Scanmonitor
{
public partial class Form1 : Form
{
FileSystemWatcher watcher = new FileSystemWatcher();
DateTime lastRead = DateTime.MinValue;
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
FileWatch();
}
public void FileWatch()
{
watcher.Path = #"C:\Scanner";
watcher.NotifyFilter = NotifyFilters.FileName | NotifyFilters.DirectoryName | NotifyFilters.LastWrite;
watcher.Filter = "*.pdf";
watcher.Changed += new FileSystemEventHandler(OnChanged);
watcher.EnableRaisingEvents = true;
}
public void OnChanged(object source, FileSystemEventArgs e)
{
scannerListBox.Items.Add(e.FullPath);
scannerListBox.SelectedIndex = scannerListBox.Items.Count - 1;
FileMove(scannerListBox.SelectedItem.ToString());
}
public void FileMove(string filePath)
{
try
{
System.IO.File.Copy(filePath, #"\\share\Data\Scans op OCE 600\" + Path.GetFileName(filePath));
}
catch (Exception ex)
{
ToolLabel.Text = ex.Message.ToString();
}
}
}
}
}
Got it working.
public void OnChanged(object source, FileSystemEventArgs e)
{
try
{
watcher.EnableRaisingEvents = false;
FileInfo objFileInfo = new FileInfo(e.FullPath);
if (!objFileInfo.Exists) return;
System.Threading.Thread.Sleep(5000);
FileInfo fileinformatie = new FileInfo(e.FullPath);
string strCreateTime = fileinformatie.CreationTime.ToString();
string strCreateDate = fileinformatie.CreationTime.ToString();
strCreateTime = strCreateTime.Remove(strCreateTime.LastIndexOf(" "));
strCreateDate = strCreateDate.Remove(0,strCreateDate.LastIndexOf(" "));
ProcessAllFiles(e.FullPath, strCreateTime, strCreateDate);
}
catch (Exception ex)
{
ToolLabel.Text = ex.Message.ToString();
}
finally
{
watcher.EnableRaisingEvents = true;
}
}

You need to keep track of files (in a collection or dictionary) that already raised an event by the FileSystemWatcher. According to MSDN
Common file system operations might raise more than one event. For example, when a file is moved from one directory to another, several OnChanged and some OnCreated and OnDeleted events might be raised. Moving a file is a complex operation that consists of multiple simple operations, therefore raising multiple events. Likewise, some applications (for example, antivirus software) might cause additional file system events that are detected by FileSystemWatcher.

public void OnChanged(object source, FileSystemEventArgs e)
{
try
{
watcher.EnableRaisingEvents = false;
FileInfo objFileInfo = new FileInfo(e.FullPath);
if (!objFileInfo.Exists) return;
System.Threading.Thread.Sleep(5000);
FileInfo fileinformatie = new FileInfo(e.FullPath);
string strCreateTime = fileinformatie.CreationTime.ToString();
string strCreateDate = fileinformatie.CreationTime.ToString();
//Ignore this, only for my file information.
strCreateTime = strCreateTime.Remove(strCreateTime.LastIndexOf(" "));
strCreateDate = strCreateDate.Remove(0,strCreateDate.LastIndexOf(" "));
ProcessAllFiles(e.FullPath, strCreateTime, strCreateDate);
}
catch (Exception ex)
{
ToolLabel.Text = ex.Message.ToString();
}
finally
{
watcher.EnableRaisingEvents = true;
}
}