Linq查询加入两个对象并计算总和

Question

我有两个对象列表，我需要加入Sku然后再计算Sum（Qty * Price）。我不确定如何做到这一点？以下是我迄今为止：

var profit = (from order in orders 
      join cost in costs 
      on order.Sku equals cost.Sku 
      select (order.Qty * cost.Price)).Sum(); 

从这里摘自：

List<Order> orders = new List <Order> 
{ 
    new Order() { Sku = "ABC", Qty = 1 }, 
    new Order() { Sku = "XYZ", Qty = 2} 
}; 

List<Cost> costs = new List <Cost> 
{ 
    new Cost() { Sku = "ABC", Price = 4.50m }, 
    new Cost() { Sku = "XYZ", Price = 2.25m } 
}; 


var profit = from order in orders 
      join cost in costs 
      on order.Sku equals cost.Sku 
      select Sum(order.Qty * cost.Price) 

Answer 1

如下更改您的最后一部分Stackoverflow question that answered how to sum