public void AddDistrict(int districtId)
 {
     if (!DistrictIds.Contains(districtId))
     {
         var a = new int[DistrictIds.Length + 1];
         DistrictIds.CopyTo(a, 0);
         a[DistrictIds.Length] = districtId;
         DistrictIds           = a;
     }
 }
 public void RemoveDistrict(int districtId)
 {
     if (DistrictIds.Contains(districtId))
     {
         var a     = new int[DistrictIds.Length - 1];
         int index = 0;
         foreach (var d in DistrictIds)
         {
             if (d != districtId)
             {
                 a[index++] = d;
             }
         }
         DistrictIds = a;
     }
 }