Program.cs

using Microsoft.Data.SqlClient;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

namespace TaxApp_v2
{
    internal static class Program
    {
        /// <summary>
        ///  The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            var host = CreateHostBuilder(new string[0]).Build();

            // Create an instance of the DatabaseManager class and create the tables.
            var dbManager = host.Services.GetRequiredService<DatabaseManager>();
            dbManager.CreateTables();

            Application.SetHighDpiMode(HighDpiMode.SystemAware);
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            ApplicationConfiguration.Initialize();
            Application.Run(new TaxAppForm());
        }
        public static IHostBuilder CreateHostBuilder(string[] args) =>
            Host.CreateDefaultBuilder(args)
                .ConfigureServices((hostContext, services) =>
                {
                    services.AddSingleton<DatabaseManager>();
                });
    }
}