Access a variable from another method

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I am having trouble accessing a FileSystemWatcher from another method.

C#

public static void watch(string path)
{
    FileSystemWatcher watcher = new FileSystemWatcher();

    watcher.Path = path;
    watcher.NotifyFilter = NotifyFilters.Attributes |
                   NotifyFilters.CreationTime |
                   NotifyFilters.DirectoryName |
                   NotifyFilters.FileName |
                   NotifyFilters.LastAccess |
                   NotifyFilters.LastWrite |
                   NotifyFilters.Security |
                   NotifyFilters.Size;
    watcher.Filter = "*.*";
    watcher.IncludeSubdirectories = true;
    watcher.Changed += new FileSystemEventHandler(OnChanged);
    watcher.Created += new FileSystemEventHandler(OnChanged);
    watcher.Deleted += new FileSystemEventHandler(OnChanged);
    watcher.Renamed += new RenamedEventHandler(OnChanged);
    watcher.EnableRaisingEvents = true;
}

private static void OnChanged(object sender, FileSystemEventArgs e)
{
    // The reason for having this try block (and EnableRaisingEvents toggling)
    // is to solve a known problem with FileSystemWatcher, in which the event
    // is fired twice.

    try
    {
        MessageBox.Show("File changed.");

        watcher.EnableRaisingEvents = false; // Error: The name 'watcher' does
                                            // not exist in the current context
    }
    finally
    {
        watcher.EnableRaisingEvents = true; // Error: The name 'watcher' does
                                           // not exist in the current context
    }
}

I want to change the EnableRaisingEvents property.

I can't do that because of the scope problem. Normally what I would do is declare the FileSystemWatcher somewhere with a bigger scope, but I can't do that here because a new one must be created every time I run the method.

So, how can I change the property of an object from a different method?

PS: I have searched around, and tried different things but ultimately nothing worked.

EDIT: Just to clarify, I MUST keep the FileSystemWatcher declaration INSIDE the method (as opposed to giving it a bigger scope, thus allowing it to be modified by another method). The reason for this is that I need a new one to be created every time I run the method.

Posted 6-May-14 13:54pm

BeginnerForLife

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Comments

PIEBALDconsult 6-May-14 20:05pm

"I need a new one to be created every time I run the method"
You can still do that even if you declare it outside the method.
(It still sounds like a weird requirement though.)

[no name] 6-May-14 21:10pm

"ultimately nothing worked", and that is as it should be.

Matt T Heffron 7-May-14 13:02pm

Did my Solution 1 help?
If so, please formally "Accept" the solution.

Looking at your code again, I'm wondering what keeps the FileSystemWatcher that is created in the watch() method from being garbage collected away? There doesn't seem to be anything that will reference it after the end of watch(). You might need to keep some collection of all such created FileSystemWatchers in a static field/property of this class.

BeginnerForLife 7-May-14 14:16pm

I have accepted your solution. Thank you very much, it worked flawlessly.

Sorry for the delay, I was not able to review your solution until just before this reply.

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Matt T Heffron · Accepted Answer · 2014-05-06T15:12:00

I'm pretty sure that the FileSystemWatcher created in the watch method will be the value of the sender parameter of the OnChanged method.
In that case, it should be pretty simple:

C#

private static void OnChanged(object sender, FileSystemEventArgs e)
{
    FileSystemWatcher watcher = sender as FileSystemWatcher;
    if (watcher == null)      // sender isn't a FileSystemWatcher
      return;                 // quit while we're behind! :-)

    // The reason for having this try block (and EnableRaisingEvents toggling)
    // is to solve a known problem with FileSystemWatcher, in which the event
    // is fired twice.

    try
    {
        MessageBox.Show("File changed.");

        watcher.EnableRaisingEvents = false; // Error: The name 'watcher' does
                                             // not exist in the current context
    }
    finally
    {
        watcher.EnableRaisingEvents = true; // Error: The name 'watcher' does
                                            // not exist in the current context
    }
}