使用左联接和if语句的实体框架查询

Question

I have two tables- workers and vehicles: Vehicle(Id, VehicleNumber) Workers(Id, Name, VehicleId)

I need to write a method that get a bool? parameter "isFree" and uses the entity framework (prefer lambda and not linq to entities) in order to:
if isFree==null then returns all vehicles
if isFree==true then returns all vehicles that doesn't belong to any worker
if isFree==false then returns all vehicles that belong to some worker

What is the best practise to solve this?

Answer 1

if(!isFree.HasValue)
  return context.Vehicles;
else if(isFree)
  return context.Vehicles.Where(v => !v.Workers.Any());
else
  return context.Vehicles.Where(v => v.Workers.Any());