In query you can use
datename()
method
string selectSQL = "select UPPER(name) as name,userid,day(dob) as da,DATENAME(month,dob) as mn,Designation,Deptt from empbirth where day (dob-1)= datepart(day, getdate()) AND month(dob)= datepart(month, getdate()) or day (dob-2)= datepart(day, getdate()) AND month(dob)= datepart(month, getdate())";