public struct MyStruct {
    string id;
}

public int main(string[] args) {
    Gtk.init(ref args);

    var mystruct = MyStruct();
    mystruct.id = "The ID";

    var model = new Gtk.ListStore(1, typeof(MyStruct));
    Gtk.TreeIter iter;
    model.append(out iter);
    model.set(iter, 0, mystruct, -1);

    MyStruct mystruct2;
    model.get(iter, 0, out mystruct2, -1);
    stdout.printf(mystruct2.id.to_string() + "\n");

    return 0;
}