Програми для обліку

using Gtk;

class Program 
{
    static void Main()
    {        
        var app = Application.New("ua.org.accounting.test", Gio.ApplicationFlags.FlagsNone);

        app.OnActivate += (sender, args) =>
        {
            FirstWindow firstWindow = new(app);
            firstWindow.Show();
        };

        app.RunWithSynchronizationContext(null);
    }
}

using Gtk;
using static Gtk.Orientation;

class FirstWindow : Window
{
    public FirstWindow(Application app) : base()
    {
        Application = app;
        Title = "Window";

        SetDefaultSize(500, 500);

        Box vBox = Box.New(Vertical, 5);
        vBox.MarginTop = vBox.MarginBottom = vBox.MarginStart = vBox.MarginEnd = 5;
        Child = vBox;
    }
}