WPF: automatically update ListView

Question

I have a ListView that shows me .txt files in a specific folder. I want the ListView to update automatically as soon as a file is added (or deleted) to that folder. I found the FileSystemWatcher class on the Internet, but I can't get the program to run properly. Anyone have any tips? I'm fairly new to C# programming.

My XAML Code:

Code-Behind:

    public partial class MainWindow : Window
{
    public string path = @"C:	xt";
    public MainWindow()
    {
        InitializeComponent();

        //Read txt Files
        DirectoryInfo d = new DirectoryInfo(path);
        FileInfo[] txtFiles = d.GetFiles();
        TxtListView.ItemsSource = txtFiles;

        MonitorDirectory(path);
    }

    public void MonitorDirectory(string path)

    {

        FileSystemWatcher fileSystemWatcher = new FileSystemWatcher();

        fileSystemWatcher.Path = path;

        fileSystemWatcher.Created += FileSystemWatcher_Created;

        fileSystemWatcher.EnableRaisingEvents = true;

    }

    private void FileSystemWatcher_Created(object sender, FileSystemEventArgs e)
    {
        DirectoryInfo d = new DirectoryInfo(path);
        FileInfo[] txtFiles = d.GetFiles();
        TxtListView.ItemsSource = txtFiles;
    }
    //Refresh-Button
    private void Refresh(object sender, RoutedEventArgs e)
    {
        DirectoryInfo d = new DirectoryInfo(path);
        FileInfo[] txtFiles = d.GetFiles();
        TxtListView.ItemsSource = txtFiles;
    }
}

user_1136211 · Answer

Here is a simple example that uses the MVVM architectural pattern.

There is a view model class that holds the FileSystemWatcher and an ObservableCollection of FileInfo objects that is used as source of a data binding in the view.

You have to take care for the fact that the events of the FileSystemWatcher are fired in a background thread, e.g. by using the EnableCollectionSynchronization method.

public class ViewModel
{
    private readonly object filesLock = new object();

    public ObservableCollection Files { get; }
        = new ObservableCollection();

    public ViewModel(string path)
    {
        BindingOperations.EnableCollectionSynchronization(Files, filesLock);

        foreach (var fileInfo in new DirectoryInfo(path).EnumerateFiles())
        {
            Files.Add(fileInfo);
        }

        var fsw = new FileSystemWatcher(path);
        fsw.Created += FileCreated;
        fsw.Deleted += FileDeleted;
        fsw.EnableRaisingEvents = true;
    }

    private void FileCreated(object sender, FileSystemEventArgs e)
    {
        lock (filesLock)
        {
            Files.Add(new FileInfo(e.FullPath));
        }
    }

    private void FileDeleted(object sender, FileSystemEventArgs e)
    {
        lock (filesLock)
        {
            var removed = Files.FirstOrDefault(fi => fi.Name == e.Name);

            if (removed != null)
            {
                Files.Remove(removed);
            }
        }
    }
}

An instance of the view model is assigned to the DataContext property of the MainWindow

public partial class MainWindow : Window
{
    public MainWindow()
    {
        InitializeComponent();

        DataContext = new ViewModel(...); // insert the directory path here
    }
}

to enable data binding in the view.

The XAML below also uses a CollectionViewSource to enable sorting.

WPF: automatically update ListView

1 Answers