How would I write this dynamic linq query? - linq

Question

Basically I want to write a linq query to order the number of days they were present. But I have got these six time filters- Today,Yesterday,current month,previous month,current year,previous year.So now I have this queries which I have simplified but before these queries below, I actually order these employees on different aspects and after ordering it as you can see I assign rank and then at the same time find out his count(which may or may not be used to rank them later)-
var result=datacontext.Employee(c=>c.Company.Id==companyId).Select((k, index) => new EmployeeDTO()
{
EmployeeId=k.Employee.Id,
CompanyId=Employee.Company.Id
PresentCount=(from e in employeeAttendance
where d.RecNum == k.recnum
&& d.date_present.Year == DateTime.Today.Year
&& d.date_present.Month == DateTime.Today.Month
&& d.date_present.Day == DateTime.Today.Day
select d).Count()
}
So now when the filter is say previous year I have -
var result=datacontext.Employee(c=>c.Company.Id==companyId).Select((k, index) => new EmployeeDTO()
{
Position=
EmployeeId=k.Employee.Id,
CompanyId=Employee.Company.Id
PresentCount=(from e in employeeAttendance
where d.RecNum == k.recnum
&& d.date_present.Year == (DateTime.Today.Year-1)
}
and if have it on Current Month I have -
var result=datacontext.Employee(c=>c.Company.Id==companyId).Select((k, index) => new EmployeeDTO()
{
EmployeeId=k.Employee.Id,
CompanyId=Employee.Company.Id
PresentCount=(from e in employeeAttendance
where d.RecNum == k.recnum
&& d.date_present.Month == DateTime.Today.Month
&& d.date_present.Year == DateTime.Today.Year
}
I basically want to combine all these in one query with basically having like a dynamic clause for finding out the present count ?

Answer 1

Just create a simple wrapper. Eg:
IQueryable<EmployeeDTO> GetEmployeeCount(Expression<Func<DateTime, bool>> pred)
{
var result=datacontext.Employee(c=>c.Company.Id==companyId).
Select((k, index) => new EmployeeDTO()
{
EmployeeId=k.Employee.Id,
CompanyId=Employee.Company.Id,
PresentCount=(from e in employeeAttendance
where d.RecNum == k.recnum && pred(d.date_present)
select d).Count()
});
return result;
}
Usage:
var r = GetEmployeeCount(d => d.Year == (DateTime.Today.Year-1));
var r = GetEmployeeCount(
d => d.Month == DateTime.Today.Month && d.Year == DateTime.Today.Year);