I am assuming that you want to retrieve all the records where date of birth is on Jan 2012 or Feb 2012. If that's the case you can use DATEPART
] to filter your rows.
SELECT COUNT(*) AS TotalRows FROM DOB
WHERE (DATEPART(Month,dateOfBirth) = 1 OR DATEPART(Month,dateOfBirth) = 2) AND (DATEPART(year,dateOfBirth) = 2012)
] might help you. Take a look at SqlFunctions.DatePart Method
Also check out this CP article LINQ query to compare only date part of DateTime