How to search or query two tables in asp.net 4.0 u

Question

I have this tables below
 
Reservation Table
 
CheckInDate datetime Unchecked
CheckOutdate datetime Unchecked
NoOfDays int Unchecked
RoomId int Unchecked
Booking_Charges float Unchecked
NoOfAdults int Checked
NoOfKids int Checked
 
room Table
 
RoomId int Unchecked
RoomType varchar(50) Unchecked
 

on my default.aspx
 
I have this
 
<asp:TextBox ID="TxtCheckIn" runat="server" > and
 
<asp:TextBox ID="TxtCheckout" runat="server" >
 
but it uses calendar control...
 
My Aim is to search the available rooms....as in to get the rooms that is not in reservation table at the particular date selected
 
How can i achieve that...
 
Thanks in advance