问选择默认的组合框值

EN

using Gtk;
using System;

class SharpApp : Window
{
    Label label;
    Label label2;
    Label label3;
    Label label4;

    public SharpApp() : base(" VALUTASOFFAN")
    {
        SetDefaultSize(411, 199);
        SetPosition(WindowPosition.Center);
        SetIconFromFile("..\\..\\web.png");

        DeleteEvent += new DeleteEventHandler(OnDelete);

        string[] valutor = new string[] 
        {    
            "YEN",
            "SEK",
            "EURO" 
        };

        //BOX1
        Fixed fix = new Fixed();
        ComboBox cb = new ComboBox(valutor);
        ComboBox cb2 = new ComboBox(valutor);
        Entry entry = new Entry ();
        Entry entry2 = new Entry ();
        cb.Changed += OnChanged;
        cb2.Changed += OnChanged2;
        entry.Changed += onChanged3;
        entry2.Changed += onChanged4;

        ComboBox combo = ComboBox.NewText(); 
        combo.Active = 0
        cb.Active = 0;

        label = new Label("-");
        label2 = new Label("-");
        label3 = new Label("-");
        label4 = new Label("-");

        fix.Put(entry, 100, 30);
        fix.Put(entry2, 100, 100);
        fix.Put(cb, 300, 30);
        fix.Put(cb2, 300, 100);
        //fix.Put(label3, 10, 30);
        //fix.Put(label4, 10, 100);
        Add(fix);

        ShowAll();      
    }

    void OnChanged(object sender, EventArgs args)
    {
        ComboBox cb = (ComboBox) sender;
        label.Text = cb.ActiveText;
    }

    void OnChanged2(object sender2, EventArgs args)
    {
        ComboBox cb2 = (ComboBox) sender2;
        label2.Text = cb2.ActiveText;
    }

    void onChanged3(object sender3, EventArgs args)
    {
        Entry entry = (Entry)sender3;
        label3.Text = entry.Text;
    }

    void onChanged4(object sender4, EventArgs args)
    {
        Entry entry2 = (Entry)sender4;
        label4.Text = entry2.Text;
    }

    public static void Main()
    {
        Application.Init();
        new SharpApp();
        Application.Run();
    }

    void OnDelete(object obj, DeleteEventArgs args)
    {
        Application.Quit();
    }
}