Chapter101:FileSystemWatcher

path                                                                                 filter

The directory to monitor, in standard or Universal Thetypeoffilestowatch.Forexample,”*.txt”watches for

Naming Convention (UNC) notation. changes to all text files.

Section101.1:IsFileReady

Thetypeoffilestowatch.Forexample,”*.txt”watches for changes to all text files.

A common mistake a lot of people starting out with FileSystemWatcher does is not taking into account That the FileWatchereventisraisedassoonasthefileiscreated.However,itmaytakesometimeforthefiletobefinished.

Example:

Take a file size of 1 GB for example . The file apr ask created by another program (Explorer.exe copying it from somewhere) but it will take minutes to finish that process. The event is raised that creation time and you need to wait for the file to be ready to be copied.

Thisisamethodforcheckingifthefileisready.

publicstaticboolIsFileReady(StringsFilename)

{

//Ifthefilecanbeopenedforexclusiveaccessitmeansthatthefile

//isnolongerlockedbyanotherprocess.

try

{

using(FileStreaminputStream=File.Open(sFilename,FileMode.Open,FileAccess.Read, FileShare.None))

{

if(inputStream.Length>0)

{

returntrue;

}

else

{

returnfalse;

}

}

}

catch(Exception)

{

returnfalse;

}

}

Section101.2:BasicFileWatcher

The following example creates a FileSystemWatcherto watch the directory specified at run time. The component is settowatchforchangesinLastWriteandLastAccesstime,thecreation,deletion,orrenamingoftextfilesinthe directory. If a file is changed, created, or deleted, the path to the file prints to the console. When a file is renamed, the old and new paths print to the console.

UsetheSystem.DiagnosticsandSystem.IOnamespacesforthisexample.

FileSystemWatcherwatcher;

privatevoidwatch()

{

//CreateanewFileSystemWatcherandsetitsproperties.

watcher=newFileSystemWatcher();

watcher.Path=path;

/*WatchforchangesinLastAccessandLastWritetimes,and therenamingoffilesordirectories.*/

watcher.NotifyFilter=NotifyFilters.LastAccess|NotifyFilters.LastWrite

|NotifyFilters.FileName|NotifyFilters.DirectoryName;

//Onlywatchtextfiles.

watcher.Filter=”*.txt*”;

//Addeventhandler.

watcher.Changed+=newFileSystemEventHandler(OnChanged);

//Beginwatching.

watcher.EnableRaisingEvents=true;

}

//Definetheeventhandler.

privatevoidOnChanged(objectsource,FileSystemEventArgse)

{

//Copiesfiletoanotherdirectoryoranotheraction.

Console.WriteLine(“File:”+                e.FullPath+””+e.ChangeType);

}