How can I query a collection of objects in LINQ as a child property?
I'm new to linq and don't know how to write two simple queries. For some reason, I can't get my head around me.
its simple structure: the order has OrderItems. each orderItem has a product ID.
I would like to:
-
get all orders that ordered productId 3
-
get all orders that ordered productId 4 AND 5 in the same order.
I've tried this in several ways. two requests are at the bottom of a small test application.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace test
{
class Program
{
static void Main(string[] args)
{
OrderService svc = new OrderService();
//find all orders that purchased ProductID 3
IEnumerable<Order> data = svc.GetOrdersWithProduct(3);
//find all orders that purchase product 4 AND 5
IEnumerable<Order> data2 = svc.GetOrdersWithProduct(new int[] { 4, 5} );
}
}
public class Order
{
public int OrderId { get; set; }
public IEnumerable<OrderItem> Items { get; set; }
}
public class OrderItem
{
public int OrderItemId { get; set; }
public int OrderId { get; set; }
public int ProductId { get; set; }
}
public class OrderService
{
private static List<Order> GetTestData()
{
List<Order> orders = new List<Order>();
//5 Orders, 3 items each (every orderitem has a unique product in this test set)
int orderitemid = 1;
int productid = 1;
for (int orderid = 1; orderid < 6; orderid++)
{
orders.Add(new Order
{
OrderId = orderid,
Items = new List<OrderItem>
{
new OrderItem() { OrderId = orderid, OrderItemId = orderitemid++, ProductId = productid ++ },
new OrderItem() { OrderId = orderid, OrderItemId = orderitemid++, ProductId = productid ++ },
new OrderItem() { OrderId = orderid, OrderItemId = orderitemid++, ProductId = productid ++ }
}
});
}
return orders;
}
public IEnumerable<Order> GetOrdersWithProduct(int productId)
{
List<Order> orders = OrderService.GetTestData();
// ?? not really what i want, since this returns only if all items are the same
var result = orders.Where(o => o.Items.All(i => i.ProductId == productId));
return result.ToList();
}
public IEnumerable<Order> GetOrdersWithProduct(IEnumerable<int> productIds)
{
List<Order> orders = OrderService.GetTestData();
//??
var result = orders.Where(o => o.Items.All(productIds.Contains(i => i.ProductId)));
return result.ToList();
}
}
}
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4 answers
I would do it like this:
-
Get all orders that ordered productId 3
var result = orders.Where(o => o.Items.Any(item => item.ProductId == 3));
-
Get all orders that ordered productId 4 and 5
var result = orders.Where(o => o.Items.Any(item => item.ProductId == 4)) .Where(o => o.Items.Any(item => item.ProductId == 5));
Or:
public static IEnumerable<Order> GetOrdersWithProduct(int id)
{
return orders.Where(o => o.Items.Any(item => item.ProductId == productId));
}
Then:
var result1 = GetOrdersWithProduct(3);
var result2 = GetOrdersWithProduct(4).Intersect(GetOrdersWithProduct(5));
Another alternative:
public static IEnumerable<Order> GetOrdersWithProducts(params int[] ids)
{
return GetOrdersWithProducts((IEnumerable<int>) ids);
}
public static IEnumerable<Order> GetOrdersWithProducts(IEnumerable<int> ids)
{
return orders.Where(o => !ids.Except(o.Items.Select(p => p.ProductId))
.Any());
}
var result1 = GetOrdersWithProducts(3);
var result2 = GetOrdersWithProduct(4, 5);
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Without Linq Language-Integrated Query Syntax:
public IEnumerable<Order> GetOrdersWithProduct(int productId)
{
List<Order> orders = OrderService.GetTestData();
var result = orders.Where(o => o.Items.Any(i => i.ProductId == productId));
return result.ToList();
}
public IEnumerable<Order> GetOrdersWithProduct(IEnumerable<int> productIds)
{
List<Order> orders = OrderService.GetTestData();
var result = orders.Where(o => productIds.All(id => o.Items.Any(i => i.ProductId == id)));
return result.ToList();
}
Let's assume The Lame Duck is running the "Language-Integrated Query" version, so I won't do that.
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public IEnumerable<Order> GetOrdersWithProduct( int productId )
{
List<Order> orders = OrderService.GetTestData( );
// ?? not really what i want, since this returns only if all items are the same
//var result = orders.Where( o => o.Items.All( i => i.ProductId == productId ) );
var result = orders.Where(o => o.Items.Any(ii => ii.ProductId == productId));
return result.ToList( );
}
0
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