private void btnImportClasses_Click(object sender, RoutedEventArgs e)
        {
            OpenFileDialog dialog = new OpenFileDialog();

            dialog.Filter = "MS Access files (*.mdb)|*.mdb";
            if (dialog.ShowDialog() == true)
            {
                if (dialog.FileName.EndsWith(".mdb"))
                {
                    try
                    {
                        BackgroundWorker worker = new BackgroundWorker();

                        worker.DoWork += (o, ea) =>
                        {
                            var classes = AccessDatabaseHelper.GetClassesFromAccess(dialog.FileName);
                            client.AddClasses(classes);
                            UpdateClassViews();
                        };

                        worker.RunWorkerCompleted += (o, ea) =>
                        {
                            this.busyIndicator.IsBusy = false;
                            MessageBox.Show("Класовете бяха импортирани успешно");
                        };

                        this.busyIndicator.IsBusy = true;
                        worker.RunWorkerAsync();
                    }
                    catch (Exception ex)
                    {
                        MessageBox.Show("Грешка при импортирането. Класовете не бяха добавени");
                    }
                }
                else
                {
                    MessageBox.Show("Програмата поддържа само MS Access файлове (.mdb)");
                }
            }
        }