The GroupJoin method is challenging to use. It requires at least 4 arguments. We can specify these Func types with the lambda expression syntax.
using System;
using System.Collections.Generic;
using System.Linq;
class Customer
{
public int Code { get; set; }
public string Name { get; set; }
}
class Order
{
public int KeyCode { get; set; }
public string Product { get; set; }
}
class Result
{
public string Name { get; set; }
public IEnumerable<Order> Collection { get; set; }
public Result(string name, IEnumerable<Order> collection)
{
this.Name = name;
this.Collection = collection;
}
}
class Program
{
static void Main()
{
// Example customers.
var customers = new Customer[]
{
new Customer{Code = 5, Name =
"Sam"},
new Customer{Code = 6, Name =
"Dave"},
new Customer{Code = 7, Name =
"Julia"},
new Customer{Code = 8, Name =
"Sue"}
};
// Example orders.
var orders = new Order[]
{
new Order{KeyCode = 5, Product =
"Book"},
new Order{KeyCode = 6, Product =
"Game"},
new Order{KeyCode = 7, Product =
"Computer"},
new Order{KeyCode = 7, Product =
"Mouse"},
new Order{KeyCode = 8, Product =
"Shirt"},
new Order{KeyCode = 5, Product =
"Underwear"}
};
// Correlate "customers" with "orders"
// ... Use Code property as key for Customer.
// ... Use KeyCode property as key for Order.
// ... For each result, create object with Name and IEnumerable of orders.
var query = customers.GroupJoin(orders,
c => c.Code,
o => o.KeyCode,
(c, result) => new Result(c.Name, result));
// Enumerate results.
foreach (var result in query)
{
Console.WriteLine(
"{0} bought...", result.Name);
foreach (var item in result.Collection)
{
Console.WriteLine(item.Product);
}
}
}
}
Sam bought...
Book
Underwear
Dave bought...
Game
Julia bought...
Computer
Mouse
Sue bought...
Shirt