Specified cast is not valid.

var newDt = dt.AsEnumerable()
               .GroupBy(r => new { name = r["name"], email = r["email"], phoneNo=
                r["phone_no"], checkIn = r["check_in"], checkOut =
                r["check_out"],noDate = r["no_date"], clientValidationCode =
                r["client_validation_code"],clientBookingType =
                r["client_booking_type"],clientPaymentGateway =
                r["client_payment_gateway"], clientCreatedAt =
                r["client_created_at"],status = r["status"]
                   })
                   .Select(g => new
                   {
                       Name = g.Key.name,
                       Email= g.Key.email,
                       PhoneNo= g.Key.phoneNo,
                       CheckIn= g.Key.checkIn,
                       CheckOut= g.Key.checkOut,
                       NoDate= g.Key.noDate,
                       ClientValidationCode= g.Key.clientValidationCode,
                       ClientBookingType= g.Key.clientBookingType,
                       ClientPaymenetGateway= g.Key.clientPaymentGateway,
                       ClientCreatedAt= g.Key.clientCreatedAt,
                       Status =g.Key.status,
                       type_no = string.Join(",", g.Select(z => z.Field<string>
                       ("room_no"))),
                       clientBookingId = g.Min(r=> r.Field<int>("client_booking_id")),
                       extraDiscount = g.Sum(r => r.Field<decimal>("extra_discount")),
                       netPrice = g.Sum(r => r.Field<decimal>("netPrice")),
                       commission = g.Sum(r => r.Field<decimal>("commission")),
                       vatOrg = g.Sum(r => r.Field<decimal>("vat_org")),
                       vatGetrest = g.Sum(r => r.Field<decimal>("vat_getrest")),
                       payed = g.Sum(r => r.Field<decimal>("payed")),
                       unPayed = g.Sum(r => r.Field<decimal>("un_payed")),

                   });