Gap in dates using c#

CREATE TABLE TESTDATE
 (
 ID int primary key identity(1,1),
 EName varchar(50),
  FromDate Datetime,
 ToDate Datetime
 )

 INSERT INTO TESTDATE VALUES('AA','2016/01/01','2016/01/31')
 INSERT INTO TESTDATE VALUES('AA1','2016/01/01','2016/03/31')


 SELECT * FROM TESTDATE WHERE FromDate BETWEEN '2016/01/01' AND '2016/03/31'

declare @startdate DATE = '2016-01-01'
declare @enddate DATE = '2016-09-30'
;with MissingDates (date)
as
(
    select @startdate
    Union All
    select dateadd(month, 1, date)
    from MissingDates
    where dateadd(month, 1, date)<=@enddate
)
select year(date) as Year, month(date) as Month
from missingDates