Lambda具有嵌套类

我刚刚发布了这个问题但得到了我的问题的部分答案，所以我想我发布了更多的解释，希望得到一个更准确的答案。 我有2个class：

public class Employee { public string Name { get; set; } public List Cars { get; set; } } public class Car { public int CarID { get; set; } public CarTypes CarType { get; set; } public enum CarTypes { Van, SmallCar } } 

我试图只获得所有使用Lambda分配了使用SmallCars忽略那些货车的员工，我尝试了这一行：

 List EmployeesWithVans = AllEmployees.Where(emps => emps.Car.Any(cartype => cartype.CarType == Car.CarTypes.Van)).ToList(); 

但如果我尝试（ .All ）至少有一辆货车被分配给员工（ .Any ），这将获得所有员工，因为并非所有员工都拥有Van，所以它将带回任何东西。

是否可以使用嵌套的Lambda实现这一点？

谢谢。

编辑：

 Employee Mark = new Employee(); Mark.Cars.Add(new Car() { CarType = Car.CarTypes.Van, CarID = 12 }); Mark.Cars.Add(new Car() { CarType = Car.CarTypes.Van, CarID = 13 }); Mark.Cars.Add(new Car() { CarType = Car.CarTypes.SmallCar, CarID = 14 }); Employee Lisa = new Employee(); Lisa.Cars.Add(new Car() { CarType = Car.CarTypes.Van, CarID = 15 }); Lisa.Cars.Add(new Car() { CarType = Car.CarTypes.SmallCar, CarID = 16 }); Lisa.Cars.Add(new Car() { CarType = Car.CarTypes.SmallCar, CarID = 17 }); List EmployeesWithVans should contain: Employee FilteredMark contains: Mark.Cars.Add(new Car() { CarType = Car.CarTypes.Van, CarID = 12 }); Mark.Cars.Add(new Car() { CarType = Car.CarTypes.Van, CarID = 13 }); Employee FilteredLisa contains: Mark.Cars.Add(new Car() { CarType = Car.CarTypes.Van, CarID = 15 }); 

Answer 1

试试这个：

 List Temp = AllEmployees.Where(emps => emps.Cars.Any(cartype => cartype.CarType == Cars.CarTypes.Van)).ToList(); List EmployeesWithVans = (from item in Temp select new Employee{ Name = item.Name, Cars = (item.Cars.Where( car => car.CarType == Cars.CarTypes.Van)).ToList() }).ToList(); 

---

这是我试过的（在LINQPAD中）：

 void Main() { List AllEmployees = new List(); List lcars1 = new List(); Cars car1 = new Cars(); car1.CarType = Cars.CarTypes.Van; lcars1.Add(car1);lcars1.Add(car1); Cars car2 = new Cars(); car2.CarType = Cars.CarTypes.SmallCar; lcars1.Add(car2); List lcars2 = new List(); lcars2.Add(car1);lcars2.Add(car2);lcars2.Add(car2); AllEmployees.Add(new Employee(){ Name="emp1", Cars = lcars1}); AllEmployees.Add(new Employee(){ Name="emp2", Cars = lcars2}); AllEmployees.Add(new Employee(){ Name="emp3", Cars = lcars1 }); AllEmployees.Add(new Employee(){ Name="emp4", Cars = lcars2}); List Temp = AllEmployees.Where(emps => emps.Cars.Any(cartype => cartype.CarType == Cars.CarTypes.Van)).ToList(); List EmployeesWithVans = (from item in Temp select new Employee{ Name = item.Name, Cars = (item.Cars.Where( car => car.CarType == Cars.CarTypes.Van)).ToList() }).ToList(); EmployeesWithVans.Dump(); } 

输出：

Answer 2

这是你想要的吗？ （所有员工至少有一辆面包车，但没有小车）

 var EmployeesWithVans = AllEmployees .Where(emps => emps.Cars.Any(cartype => cartype.CarType == Cars.CarTypes.Van) && !emps.Cars.Any(cartype => cartype.CarType == Cars.CarTypes.SmallCar)) .ToList(); 

Answer 3

查询是正确的，如果为其分配了面包车，它会在返回序列中添加一个Employee 。 我不太确定问题出在哪里，你认为你的查询没有任何回报，因为并非所有员工都有货车吗？ 如果是，这将是Where运算符的实现：

 foreach(var elem in input) { if (predicate(elem)) yield return elem; } 

谓词将应用于序列中的所有元素，如果元素满足它，它将作为序列的一部分返回。