Disposing of FileSystemWatcher

ShaneKm picture ShaneKm · Nov 3, 2015 · Viewed 7.2k times · Source

So my understanding is that whenever using a class that implements IDisposable, it's parent also needs to implement IDisposable interface. (FileWatcher using FileSystemWatcher)

So when using FileSystemWatcher what is the proper way of disposing of FileSystemWatcher? I want FileWatcher not to be disposed/(watching) until application is closed.

Would I use Responsible Owner Pattern?(try/finally) or something else? Should my FileWatcher also implement IDisposable? I won't be able to use using{} since this fileWatcher should be watching the file changes the whole time application runs. What is the proper way of handling this scenario?

public class FileWatcher : IFileWatcher
{
    private FileSystemWatcher watcher;

    public event EventHandler<EventArgs> SettingsChanged;

    public FileWatcher(bool start)
    {
        this.RegisterForChanges();
    }

    public void OnChanged(object source, EventArgs e)
    {
        if (this.SettingsChanged != null)
        {
            this.SettingsChanged(source, new EventArgs());
        }
    }

    private void RegisterForChanges()
    {
        /// more code here etc
        ...
        this.watcher = new FileSystemWatcher
                           {
                               Path = directory, 
                               NotifyFilter =
                                   NotifyFilters.LastAccess | NotifyFilters.LastWrite
                                   | NotifyFilters.FileName | NotifyFilters.DirectoryName, 
                               Filter = fileName
                           };

        // Add event handlers.
        this.watcher.Changed += this.OnChanged;

        // Begin watching.
        this.watcher.EnableRaisingEvents = true;
    }

Answer

xxbbcc picture xxbbcc · Nov 3, 2015

Yes, implementing IDisposable is the right solution in this case (in my opinion). Your object is long-lived and has to live outside the scope of any particular function call so all function-scope level solutions (using, try..finally, etc.) are out.

For this, IDisposable is a standard pattern in .NET and you can easily dispose of the nested object when FileWatcher is disposed of.