Filesystemwatcher causing "Error too many changes at once in directory C:\"

Question

Like a few others I'm getting the error "Error too many changes at once in directory C:\" from the filesystemwatcher when he does its job. Now if it is c:\ it is clear that there are many changes. BUT in this special case I set the following parameters:

Path = C:\
Filter = "test1.txt"
NotifyFilter = NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName
IncludeSubdirectories = true

I started the watcher and let it run without problems for 4 hours after which Í locked the pc and came back a short while later and suddenly had the error.

Now I'm wondering what could have caused the error in this case. Am I overlooking something important here? OR could it be taht the includesubdirectories parameter lets it check ALL subdirectories of c:\ and ignoring the filter of the single file that exists in C:\ ?

Answer 1

You can increase the Buffer for changes - this helped me once.

But to look for every change at C:\ with subdirs can maybe cause a lot of workload..

MSDN FileSystemWatcher.InternalBufferSize Property

EDIT:

The Filter gets only checked at the Raising-Method - so internally every change gets recognized by the class.

I took a look into the framework code as you can see the main raising method .....

    private void NotifyFileSystemEventArgs(int action, string name)
    {
        if (this.MatchPattern(name))
        {
            switch (action)
            {
                case 1:
                    this.OnCreated(new FileSystemEventArgs(WatcherChangeTypes.Created, this.directory, name));
                    return;

                case 2:
                    this.OnDeleted(new FileSystemEventArgs(WatcherChangeTypes.Deleted, this.directory, name));
                    return;

                case 3:
                    this.OnChanged(new FileSystemEventArgs(WatcherChangeTypes.Changed, this.directory, name));
                    return;
            }
        }
    }

is using this method: "this.MatchPattern(name)" - which look like this:

    private bool MatchPattern(string relativePath)
    {
        string fileName = System.IO.Path.GetFileName(relativePath);
        return ((fileName != null) && PatternMatcher.StrictMatchPattern(this.filter.ToUpper(CultureInfo.InvariantCulture), fileName.ToUpper(CultureInfo.InvariantCulture)));
    }

and as you can see - the filter get checked here - far to late to have suppressed load... ...So the only way is to increase the buffer size!