Вывести цену автомобиля

using System;
using System.Collections.Generic;
using System.Data;
using System.Linq;
using System.Windows.Forms;
 
namespace WindowsFormsApp96
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
 
            // Заполняем comboBox1 марками
            CarsStorage._ListCars.Select(x => x.Brand).Distinct().ToList().ForEach(_ => comboBox1.Items.Add(_));
 
            // Заполняем comboBox2 типами кузова
            CarsStorage._ListCars.Select(x => x.TypeBody).Distinct().ToList().ForEach(_ => comboBox2.Items.Add(_));
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            double SumForSeveralCar = CarsStorage._ListCars.Where(w => w.Brand == comboBox1.SelectedItem.ToString() && w.TypeBody == comboBox2.SelectedItem.ToString())
                                                           .Select(s => s.Price * Convert.ToInt32(textBox1.Text)).FirstOrDefault();
 
            textBox2.Text = SumForSeveralCar.ToString();
        }
    }
 
    public struct Cars
    {
        public string Brand { get; set; }
        public string TypeBody { get; set; }
        public double Price { get; set; }
    }
 
    public static class CarsStorage
    {
        public static List<Cars> _ListCars = new List<Cars>()
        {
            new Cars{ Brand = "Mercedes", TypeBody = "sedan", Price = 100000 },
            new Cars{ Brand = "Mercedes", TypeBody = "coupe", Price = 120000 },
            new Cars{ Brand = "Mercedes", TypeBody = "pickup", Price = 150000 },
            new Cars{ Brand = "BMW", TypeBody = "sedan", Price = 90000 },
            new Cars{ Brand = "BMW", TypeBody = "coupe", Price = 100000 },
            new Cars{ Brand = "BMW", TypeBody = "pickup", Price = 110000 },
            new Cars{ Brand = "Audi", TypeBody = "sedan", Price = 80000 },
            new Cars{ Brand = "Audi", TypeBody = "coupe", Price = 90000 },
            new Cars{ Brand = "Audi", TypeBody = "pickup", Price = 100000 }
        };
    }
}