Invoice-App/Program.cs

using Avalonia;
using System;
using Invoice_App.Models;

namespace Invoice_App;

class Program
{
    // Initialization code. Don't use any Avalonia, third-party APIs or any
    // SynchronizationContext-reliant code before AppMain is called: things aren't initialized
    // yet and stuff might break.
    [STAThread]
    public static void Main(string[] args)
    {
        TestVehicleClass();

        BuildAvaloniaApp()
            .StartWithClassicDesktopLifetime(args);
    }


    private static void TestVehicleClass()
    {
        var testCar = new Vehicle();
        testCar.Make = "BMW";
        testCar.Model = "320i";
        testCar.VinNumber = "ABC123";
        testCar.Kilometers = 50000;
        testCar.RegistrationDate = DateTime.Now;
        testCar.Comments = "Good condition";

        // Test Company
        var testCompany = new Company();
        testCompany.CompanyName = "ABC Motors";
        testCompany.Address = "Kongens Nytorv 1";
        testCompany.ZipCode = "1050"; // Copenhagen K
        testCompany.City = "Copenhagen";
        testCompany.CVR = "12345678";
        testCompany.PhoneNumber = "33123456";

        // Test Customer  
        var testCustomer = new Customer();
        testCustomer.Name = "Lars Nielsen";
        testCustomer.Address = "Vesterbrogade 123";
        testCustomer.ZipCode = "1620";
        testCustomer.City = "Copenhagen V";
        testCustomer.PhoneNumber = "23456789";
        testCustomer.Email = "lars@example.com";
    }


    // Avalonia configuration, don't remove; also used by visual designer.
    public static AppBuilder BuildAvaloniaApp()
        => AppBuilder.Configure<App>()
            .UsePlatformDetect()
            .WithInterFont()
            .LogToTrace();
}