Issue was with my data. In dataset I was fetching rows based on Isnull() like below
WHEN 'Y'='Y' THEN ISNULL(Code ,'') + ' ' + ISNULL(Description ,'')
WHEN ISNULL(Code ,'')='' THEN ISNULL(RefCharge ,'')
+' '+ISNULL(RefDescription ,'')
ELSE ISNULL(Code ,'')+' '+ISNULL(Description ,'')
END AS Details
So it was showing (3 blank spaces) and my expression was.