BlueSky.Windows.AddFactorLevelsDialog.addlvlButton_Click C# (CSharp) Метод

        private void addlvlButton_Click(object sender, RoutedEventArgs e)
        {
            string newlevel = faclvltxt.Text.Trim();
            if (newlevel == null || newlevel.Length < 1)//Blanks not allwed as factors
            {
                MessageBox.Show("Blank Spaces Not Allowed! ","Blank Level", MessageBoxButton.OK, MessageBoxImage.Warning);
            }
            else if (!isDuplicate(newlevel))
            {
                FactorLevels.Add(newlevel);
                levelsListBox.ItemsSource = null;
                levelsListBox.ItemsSource = FactorLevels;
                levelsListBox.SelectedItem = newlevel;
                levelsListBox.ScrollIntoView(newlevel);
                
                faclvltxt.Text = string.Empty;
            }
            else
            {
                MessageBox.Show("Duplicate Level Not Allowed! ", "Duplicate Level", MessageBoxButton.OK, MessageBoxImage.Warning);
            }
        }