private void btnOk_Click(object sender, RoutedEventArgs e)
        {
            nameTextBox.GetBindingExpression(TextBox.TextProperty).UpdateSource();
            descriptionTextBox.GetBindingExpression(TextBox.TextProperty).UpdateSource();
            startDateTextBox.GetBindingExpression(TextBox.TextProperty).UpdateSource();
            repeatedCheckBox.GetBindingExpression(CheckBox.IsCheckedProperty).UpdateSource();
            repeatIntervalTextBox.GetBindingExpression(TextBox.TextProperty).UpdateSource();

            if (!_reminder.HasError())
            {
                if (_isNew)
                {
                    _remindersManager.AddReminder(_reminder);
                }
                else
                {
                    Reminder.Copy(_reminder, _reminderToEdit);
                }

                this.Close();
            }
        }