public static void DoProc()
{
var products = new List <Product4>();
var productA = new Product4()
{
Description = "aaa", Price = 100
};
var productB = new Product4()
{
Description = "bbb", Price = 200
};
var productC = new Product4()
{
Description = "ccc", Price = 300
};
products.Add(productA);
products.Add(productB);
products.Add(productC);
string[] popularProductNames = { "aaa", "bbb" };
var popularProducts = from p in products
join n in popularProductNames
on p.Description equals n
select p;
// like as inner join, ccc is not extract.
foreach (var popularProduct in popularProducts)
{
Console.WriteLine(popularProduct.Description);
}
}
public static void DoProc()
{
var productA = new Product4()
{
Description = "aaa", Price = 100
};
var productB = new Product4()
{
Description = "bbb", Price = 200
};
var productC = new Product4()
{
Description = "ccc", Price = 300
};
var orders = new List <Order4>()
{
new Order4()
{
OrderLine = new List <OrderLine4>()
{
new OrderLine4()
{
Amount = 10,
Product = productA
},
new OrderLine4()
{
Amount = 20,
Product = productB
},
},
},
new Order4()
{
OrderLine = new List <OrderLine4>()
{
new OrderLine4()
{
Amount = 30,
Product = productA
},
new OrderLine4()
{
Amount = 40,
Product = productB
},
new OrderLine4()
{
Amount = 50,
Product = productC
},
},
},
};
var averageNumberOfOrderLines =
orders.Average(o => o.OrderLine.Count);
// 2 + 3 / 2 = 2.5
Console.WriteLine(averageNumberOfOrderLines);
// group by
var result = from o in orders
from l in o.OrderLine
group l by l.Product // product is key, summary by same instance
into p
select new
{
Product4 = p.Key,
Amount = p.Sum(x => x.Amount),
};
foreach (var p in result)
{
Console.WriteLine($"{p.Product4.Description} summary is {p.Amount}.");
}
}