Question

Below is my code for a File watcher class I wrote:

class FileWatcher  
{  
    #region Method that begins watching  
    public static void watch()  
    {

        FileSystemWatcher watcher = new FileSystemWatcher();

        watcher.Path = ConfigurationManager.AppSettings["OpticusFileLoc"];
        watcher.Filter = ConfigurationManager.AppSettings["OpticusFileName"];

        watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName;

        watcher.Changed += new FileSystemEventHandler(OnChanged);
        Console.Write("\nWatcher started. Press any key to end.\n");

        watcher.EnableRaisingEvents = true;
    }
    #endregion

    #region Trigger function on change
    public static void OnChanged(object source, FileSystemEventArgs e)
    {
        Console.WriteLine("File has been changed.\n");
        //watcher.EnableRaisingEvents = false ;

        //Program.Main();
    }
    #endregion

}

How can I, from the OnChanged method, set the watcher.EnableRaisingEvents flag to false?

I guess I could do it by moving the declaration of the FileSystemWatcher object outside the method it is in, but I’m wondering if there’s another way to do it.

Answer 1

I guess I could do it by moving the
declaration of the FileSystemWatcher
object outside the method it is in,
but I’m wondering if there’s another
way to do it.

That’s exactly how you should do it (have watcher just be a member field of your FileWatcher class).

That said, you also could do it like this:

public static void OnChanged(object source, FileSystemEventArgs e)
{
    Console.WriteLine("File has been changed.");

    var watcher = source as FileSystemWatcher;
    if (watcher != null)
    {
        watcher.EnableRaisingEvents = false;
    }
    else
    {
        // Hmm... some other object called this method.
        // Do you really want that to be allowed?
    }
}

Notice the comment I added in the code above. Generally it’s a bad call to make methods such as this public, as this makes it possible for any arbitrary code to call OnChanged even when doing so makes no sense. (You want for this method to capture the event of a file being changed; if it’s actually callable from anywhere, then how do you know if the file was in fact changed or if this is just some random call from elsewhere?)