EF 6 get two after two before - entity-framework

Question

Let's say I am executing a search in for in DbContext.Cars where x=> x.Id = 1. I would like to do that and then grab two Cars after and two Carsbefore.
How would I do that?

Answer 1

Linq is just using the logic you tell it. So you just change the logic.
DbContext.Cars.Where(car => car.Id >=1 && car.Id <= 5);
The previous gets all car = 3, plus cars 1 and 2, and 4 and 5. So you could also write that:
var carNum = 3;
DbContext.Cars.Where(car => car.Id >= carNum-2 && car.Id <= carNum + 2);
This of course assumes that cars are ordered in numerical order, which you can do in your query. And that there are no missing id's. You could also do this:
DbContext.Cars.Where(/*logic to find first record, subtracting 2*/).Take(5);
In the above, you figure out some logic to find out what your first car is, then figure out what car -2 is, then you take 5 cars, which gets the 2 previous, the car you want, and the two after.
Since you did not provide enough information to determine how your data model works, this is really the best we can do, is give you information to help you figure out the logic yourself.

Answer 2

If you're sure that Id is an integer, you could do the following:
DbContext.Cars.Where(car => Math.Abs(1 - car.Id) <= 2);
If your id sequence has gaps and you want to ensure that you always get the 2 cars with the closest Ids greater than and less than your specified value, you can do:
var carNum = 6;
DbContext.Cars
.Where(car => car.Id < carNum)
.OrderByDescending(car => car.Id)
.Take(2)
.Union(DbContext.Cars
.Where(car => car.Id > carNum)
.OrderBy(car => car.Id)
.Take(2)
)
// If you'd like to also get the car with Id == carNum, uncomment the following
// .Union(DbContext.Cars.Where(car => car.Id == carNum))
;