public static List<District> ListDistrict(int? cityId, int? districtId, bool insertAllItem)
 {
     List<District> result = new DataLayer().ListDistrict(cityId, districtId);
     if (insertAllItem)
     {
         District rt = new District();
         rt.Name = "Tất cả";
         result.Insert(0, rt);
     }
     return result;
     //return new DataLayer().ListDistrict(cityId, districtId);
 }
 public static List<RealestateType> ListRealestateType(bool insertAllItem)
 {
     List<RealestateType> result = new DataLayer().ListRealestateType();
     if (insertAllItem)
     {
         RealestateType rt = new RealestateType();
         rt.Name = "Tất cả";
         result.Insert(0, rt);
     }
     return result;
 }