Catalog/imagecatalog/Program.cs

using ImageCatalog;
using ImageCatalog_2.Services;
using Microsoft.Extensions.DependencyInjection;

namespace ImageCatalog_2
{
    static class Program
    {
        public static IServiceProvider ServiceProvider { get; private set; }
        [STAThread]
        static void Main()
        {
            Application.SetHighDpiMode(HighDpiMode.SystemAware);
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);

            var serviceCollection = new ServiceCollection();
            ConfigureServices(serviceCollection);

            ServiceProvider = serviceCollection.BuildServiceProvider();

            var mainForm = ServiceProvider.GetRequiredService<MainForm>();
            var mainViewModel = ServiceProvider.GetRequiredService<DataModel>();

            mainForm.Model = mainViewModel;          

            Application.Run(mainForm);
        }

        private static void ConfigureServices(ServiceCollection services)
        {
            // Register your services here
            services.AddTransient<ITestService, TestService>();

            services.AddTransient<DataModel>();

            // Register your forms
            services.AddTransient<MainForm>();
        }
    }
}