How to release a file locked by filesystemwatcher?

private void btnEdit_Click(object sender, RoutedEventArgs e)
        {
            if (!File.Exists(lastImage)) return;
            FileSystemWatcher izleyici = new FileSystemWatcher(System.IO.Path.GetDirectoryName( lastImage),
                System.IO.Path.GetFileName(lastImage));
            izleyici.Changed += izleyici_Changed;
            izleyici.NotifyFilter = NotifyFilters.LastWrite;
            izleyici.EnableRaisingEvents = true;
            ProcessStartInfo info = new ProcessStartInfo();
            info.FileName = lastImage;
            info.Verb = "edit";
            Process.Start(info);
        }

        void izleyici_Changed(object sender, FileSystemEventArgs e)
        {
           //I want to add code here to release the file. Dispose() not worked for me

           setImageSource(lastImage);
        }

        void setImageSource(string file)
        {
            var bitmap = new BitmapImage();

            using (var stream = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.Read))
            {
                bitmap.BeginInit();
                bitmap.CacheOption = BitmapCacheOption.OnLoad;
                bitmap.StreamSource = stream;
                bitmap.EndInit();
            }

            ssreview.Source = bitmap;
        }