Считывание данных из XML файла их сложение и вывод в TextBox

public partial class Form2 : Form
 
    {
        private readonly string TemplateFileName = @"C:/Users/Oberleutnant/Desktop/Reports/template.docx";
        XDocument doc;
        public Form2()
        {
            InitializeComponent();
            doc = XDocument.Load("C:/Users/Oberleutnant/Desktop/Курсовая/Курсовая/WindowsFormsApp1/WindowsFormsApp1/XMLFile1.xml");
            IEnumerable<XElement> elements = doc.XPathSelectElements("/SpareParts/SpareEngine/SpareName");
            foreach (XElement el in elements)
            checkedListBox1.Items.Add(el.Value.Trim());
        }
        private void checkedListBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (checkedListBox1.SelectedIndex != -1)
            {
                IEnumerable<XElement> description = from node in doc.Element("SpareParts").Elements("SpareEngine")
                                                    where node.Element("SpareName").Value.Trim() == checkedListBox1.SelectedItem.ToString()
                                                    select node;
                if (description.Count() == 0)
                    textBox10.Clear();
                else
                    textBox10.Text = description.First().Element("Price").Value.Trim();
            }
            else
                textBox10.Clear();

int summa = 0;

  textBox10.Text = description.First().Element("Price").Value.Trim();

 int price = Convert.ToInt32(description.FirstOrDefault().Element("Price").Value.Trim());             
                    summa += price; 
                    textBox1.Text = summa.ToString();

public class SpareEngine
{
    public string SpareName { get; set; }
    public decimal Price { get; set; }
}

public Form2()
{
    var overrides = new XmlAttributeOverrides();
    overrides.Add(typeof(SpareEngine[]), new XmlAttributes() { XmlRoot = new XmlRootAttribute("SpareParts") });
 
    var serializer = new XmlSerializer(typeof(SpareEngine[]), overrides);
    SpareEngine[] parts;
    using (var stream = File.OpenRead("C:/Users/Oberleutnant/Desktop/Курсовая/Курсовая/WindowsFormsApp1/WindowsFormsApp1/XMLFile1.xml"))
        parts = serializer.Deserialize(stream) as SpareEngine[];
 
    checkedListBox1.DataSource = parts;
    checkedListBox1.DisplayMember = nameof(SpareEngine.SpareName);
}
 
private void checkedListBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    var list = sender as CheckedListBox;
    if (list == null)
        textBox1.Clear();
    else
    {
        var part = list.SelectedItem as SpareEngine;
        textBox1.Text = part.Price.ToString();
    }
}