Question

i like to add controls inside the form1 where a event handler for
watcher.Changed += new FileSystemEventHandler(OnChanged); is defined , is it possible to add control for example list box to the form1 but need to be added inside the event handler where it is defined

  /*event added*/ 

   private void btn_start_Click(object sender, EventArgs e)
    {
        string[] args = {this.txtfolder.Text};
        if (args.Length != 1)
        {
            // Display the proper way to call the program.
            Console.WriteLine("Usage: Invalid Operation");
            return;
        }

        FileSystemWatcher watcher = new FileSystemWatcher();
        watcher.Path = args[0];
        /* Watch for changes in LastAccess and LastWrite times, and
           the renaming of files or directories. */
        watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite
           | NotifyFilters.FileName | NotifyFilters.DirectoryName;
        // Only watch text files.
        watcher.Filter = this.txtfilter.Text;//"*.txt";

        // Add event handlers.
        watcher.Changed += new FileSystemEventHandler(OnChanged);
        watcher.Created += new FileSystemEventHandler(OnChanged);
        // watcher.Deleted += new FileSystemEventHandler(OnChanged);
        watcher.Renamed += new RenamedEventHandler(OnRenamed);



   // Define the event handlers.
    private static void OnChanged(object source, FileSystemEventArgs e)
    {
        // Specify what is done when a file is changed, created, or deleted.
        //Console.WriteLine("File: " + e.FullPath + " " + e.ChangeType);

        //   Form1 F   ;        
       // ListBox lst = new ListBox();
        //lst.Items.Add("File: " + e.FullPath + " " + e.ChangeType.ToString());
        //f.lsttracker.Items.Add("File: " + e.FullPath + " " + e.ChangeType.ToString());
       // F.controls.Add(lst);

Answer 1

This is what your looking for. From what you commented out, you probably didn’t set the location and size, thus adding the control probably wasn’t working. But you should really make sure to regulate this and make sure you are only adding controls exactly when you want to and no more.

private static void OnChanged(object source, FileSystemEventArgs e)
{
    ListBox toAdd = new ListBox();
    toAdd.Location = new Point(20,20);
    toAdd.Size = new Size(200,200);
    this.Controls.Add(toAdd);
}

If you want to store the controls you added, try something like this:

private List<Control> AddedItems = new List<Controls>();
private int OffsetY = 0;
private static void OnChanged(object source, FileSystemEventArgs e)
{
    ListBox toAdd = new ListBox();
    if(AddedItem.Last().Point.Y == OffsetY) // just an example of reusing previously added items.
    {
         toAdd.Location = new Point(20, OffsetY);
         toAdd.Size = new Size(200,200);
         AddedItems.Add(toAdd);
         this.Controls.Add(toAdd);
    }
    OffsetY += 200;
}

EDIT: In reply to what you mentioned in the comment below.

    [PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
    private void btn_start_Click(object sender, EventArgs e)
    {
        string FolderPath = this.txtfolder.Text;
        string Filter = this.txtfilter.Text;
        if(!Directory.Exists(FolderPath))
        {
            Console.WriteLine("Not a valid directory"); //checks directory is valid
            return;
        }

        FileSystemWatcher watcher = new FileSystemWatcher();

        watcher.Path = FolderPath;
        watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite
                               | NotifyFilters.FileName | NotifyFilters.DirectoryName;
        // Only watch filter files.
        watcher.Filter = Filter;

        watcher.IncludeSubdirectories = true; //monitor subdirectories?
        watcher.EnableRaisingEvents = true; //allows for changed events to be fired.

        // Add event handlers.
        watcher.Changed += new FileSystemEventHandler(OnChanged);
        watcher.Created += new FileSystemEventHandler(OnChanged);
    }
    //Delegate to get back to UI thread since OnChanged fires on non-UI thread.
    private delegate void updateListbox(string context);
    private void OnChanged(object source, FileSystemEventArgs e)
    {
        this.Invoke(new updateListbox(UpdateListbox), "File: " + e.Name);
        this.Invoke(new updateListbox(UpdateListbox), ">>Action: " + e.ChangeType);
        this.Invoke(new updateListbox(UpdateListbox), ">>Path: " + e.FullPath);
    }
    public void UpdateListbox(string context)
    {
        lsttracker.Items.Add(context);
    }