Question

我有以下内容：

IEnumerable<Corporations> Corps = ...

public class Corporation
{
    public string CompanyName { get; set; }
    public virtual ICollection<Cars> Cars { get; set; }
}

public class Car
{
    public int CarID { get; set; }
    public string CarName { get; set; }
}

如果我的CarID = 4，如何使用linq获取CarName和Company名称。

我想我已经接近了.foreach（这是旧学校？）但是却迷失了它：

var result = Corps.Where(cps => cps.Cars != null).ToList()
                .ForEach(x => x.Cars.ToList()
                    .ForEach(cr => cr.CarID == 5)
                        .Select (@y => new { FoundCorp = x.CompanyName, FoundCar = cr.CarName}....

Answer 1

下面的代码返回匿名类实例，其中包含属性Cars，其中包含与此汽车匹配的汽车项目条件和Corps属性。

var results = Corps
    .SelectMany(corp => corp.Cars, (corps, cars) => new { Corps = corps, Cars = cars })
    .Where(item => item.Cars.CarID == 4)
;

foreach (var item in results)
{
    Console.WriteLine("Car with id {0} have found in for company {1}", item.Cars.CarID, item.Corps.CompanyName);
}

您可能希望将此匿名类替换为仅包含CarName和CompanyName的特定类。只需替换实例，如下所示：

var results = Corps
    .SelectMany(corp => corp.Cars, (corps, cars) => new SomeResult(corps.CompanyName, cars.CarName))
    .Where(item => item.Cars.CarID == 4)
;

此代码对于找到的汽车/公司数量是安全的。

Answer 2

 var check = Corporation.SelectMany(p => p.Cars.Where(m => m.CarID  == "4").Select(n => new
            {
                n.CarName,
                p.CompanyName
            }));

Answer 3

你想找到任何一辆车与你的CarId =＆gt;

匹配的公司

int carid = 1;
var corp = Corps.FirstOrDefault(corp => corp.Cars.Any(car => car.CarID == carid));

if (Corp != null)
{
    Console.WriteLine(Corp.CompanyName);
    Console.WriteLine(Corp.Cars.First(car => car.CarID == carid).CarName);
}

根据Smudge的说明，如果你想确保你的CarId是唯一的，你可以考虑使用HashTable或类似的。

Linq根据IEnumerable属性选择

3 个答案: