Програми для обліку

using Gtk;

class Program
{
    public static void Main()
    {
        Application.Init();
        new FirstWindow();
        Application.Run();
    }

    public static void Quit()
    {
        Application.Quit();
    }
}

using Gtk;

class FirstWindow : Window
{
    ComboBoxText comboBoxText = new ComboBoxText();

    public FirstWindow() : base("Test")
    {
        SetDefaultSize(600, 350);
        SetPosition(WindowPosition.Center);

        DeleteEvent += delegate { Program.Quit(); };

        VBox vBox = new VBox();
        Add(vBox);

        comboBoxText.Changed += OnChanged;

        //Button
        {
            HBox hBox = new HBox();
            vBox.PackStart(hBox, false, false, 5);

            Button buttonAdd = new Button("Додати");
            buttonAdd.Clicked += OnAddClick;
            hBox.PackStart(buttonAdd, false, false, 5);

            Button buttonClear = new Button("Очистити");
            buttonClear.Clicked += OnClearClick;
            hBox.PackStart(buttonClear, false, false, 5);
        }

        //ComboBoxText
        {
            HBox hBox = new HBox();
            vBox.PackStart(hBox, false, false, 5);

            hBox.PackStart(comboBoxText, false, false, 5);

            for (int i = 1; i <= 10; i++)
                comboBoxText.Append($"{i}", $"{DateTime.Now.ToString("HH:mm:ss")} - {i}");

            comboBoxText.ActiveId = "5";
        }

        ShowAll();
    }

    void OnAddClick(object? sender, EventArgs args)
    {
        comboBoxText.Append("0", $"{DateTime.Now.ToString("HH:mm:ss")} - text");
    }
    void OnClearClick(object? sender, EventArgs args)
    {
        comboBoxText.RemoveAll();
    }
    void OnChanged(object? sender, EventArgs args)
    {
        Console.WriteLine(comboBoxText.ActiveId);
    }
}