protected void QueryPanel1_ListRequest(object sender,
                   Korzh.EasyQuery.WebControls.ListRequestEventArgs e) {
    EntityAttr countryAttr =
        query.Model.EntityRoot.FindAttribute(EntityAttrProp.Expression, "Customers.Country");
    if (e.ListName == "RegionList") {
        e.ListItems.Clear();
        string country = query.GetOneValueForAttr(countryAttr);
 
        if (country == "Canada") { 
            e.ListItems.Add("British Columbia", "BC");
            e.ListItems.Add("Quebec", "Quebec");
        }
        else if (country == "USA") {
            e.ListItems.Add("California", "CA");
            e.ListItems.Add("Colorado", "CO");
            e.ListItems.Add("Oregon", "OR");
            e.ListItems.Add("Washington", "WA");
    }
}