[SerializableAttribute()] 
public class GroupShopRelationCollection : System.Collections.ObjectModel.Collection<GroupShopRelation> 

class MyPage : System.Web.UI.Page
{
   private GroupShopRelationCollection LoadGroupShopRelations()
   {
       GroupShopRelationCollection allRelations = new GroupShopRelationCollection();
       using (IDataReader relationReader = Database.CreateDataReader("SELECT * FROM EcomShopGroupRelation", "Ecom.mdb"))
       {
           while (relationReader.Read())
           {
               GroupShopRelation relation = new GroupShopRelation(relationReader);
               allRelations.Add(relation);
           }
       }
       return allRelations;
   }
}