问题
I have two classes:
public class Person
{
public int Id{get;set;}
public string Name{get;set;}
public List<Order> Orders{get;set;}
}
public class Order
{
public int Id{get;set;}
public string Data{get;set;}
public decimal Sum{get;set;}
}
I use Nhibernate Linq. If I want to get total sum of orders filtering by Persan.Name I do this:
var result = (from person in personRepository.Query
from order in person.Orders
where person.Name.Contains("off")
select order).Sum(order => order.Sum);
How can I do the same using fluent syntax?
回答1:
Try this:
var result = personRepository.Query
.Where(person => person.Name.Contains("off"))
.SelectMany(person => person.Orders)
.Sum(order => order.Sum);
If this solution throws an ArgumentNullException
when there are no orders selected try this two step solution:
var orders = personRepository.Query
.Where(person => person.Name.Contains("off"))
.SelectMany(person => person.Orders);
var result = orders.Any()
: orders.Sum(order => order.Sum)
? 0;
来源:https://stackoverflow.com/questions/13171394/linq-select-property-collection