LINQ：查询集合中的集合

Question

我有以下结构：

public class Customer
{
  public int ID { get; set; }
  public List<Order> Orders { get; set; }
}

public class Order
{
  public int ID { get; set; }
  public int ProductID { get set; }
}

我需要获取订购 ProductID = 6 的客户的集合。流畅风格的 LINQ 会是什么样子？

我尝试了下面但没有运气：

var customers = allCustomers.SelectMany(c => c.Orders.Select(o => o.ProductID.Equals(6))).ToArray();

Answer 1

varcustomers = allCustomers.Where(c => c.Orders.Any(o => o.ProductID == 6));

Answer 2

allCustomers.Where(c => c.Orders.Any(o => o.ProductID == 6))

Answer 3

var customers = allCustomers.Where(c => c.Orders.Any(o => o.ProductID == 6));

Answer 4

看起来你想要：

var query = allCustomers.Where(c => c.Orders.Any(o => o.ProductID == 6));

Answer 5

一个很好的方法是从另一边尝试像这样

var customers from p in Order where p.ProductId == 6 select p.Customer

当然你需要在 Order 类中添加 Customer 属性，如下所示

public class Order
{
  public int ID { get; set; }
  public int ProductID { get set; }
  public Customer Customer { get; set; }
}