How to check available hotel room's C# and SQL

Question

I am making a hotel reservation system in windows form.User book hotel room by selecting hotel id and by giving a check in ,check out date.Now i want to retreive the room id's from tblRoom those are not in tblReservation(i mean the rooms that are not booked yet) and also the room id's those are in tblReservation but not between the check in,check out date.can you help me?