Question

我在每个订单中有一个订单数组是一个项目数组。如何按项目名称对所有订单进行分组，并获取订购商品的总和。在这种情况下，输出将是：

输出

Item01 : quantity = 2;
Item02 : quantity = 45;

GetOrders

public Order[] GetOrders()
{
   Order[] orders = new Order[]
      {
         new Order
            {
               id = 1,
               orderLines = new OrderLine[]
                  {
                     new OrderLine
                        {
                           itemName = "Item 01",
                           quantity = 1
                        },
                     new OrderLine
                        {
                           itemName = "Item 02",
                           quantity = 3
                        },
                  },
            },
         new Order
            {
               id = 2,
               orderLines = new OrderLine[]
                  {
                     new OrderLine
                        {
                           itemName = "Item 01",
                           quantity = 1
                        },
                     new OrderLine
                        {
                           itemName = "Item 02",
                           quantity = 42
                        }
                  }
            }
      };
      ...

我尝试了以下内容：

foreach (var order in orders)
{
   foreach (var orderline in order.orderLines.GroupBy(x => x.itemName).Select(group => new
      {
         Metric = group.Key,
         Count = group.Count()
      }))

   {
      Console.WriteLine("{0} {1}", orderline.Metric, orderline.Count);
   }
}

但它只为每个项目返回1。我对编程比较陌生，所以对我来说很容易。谢谢

Answer 1

要获取所有订购商品的总和，请使用以下查询：

var results = 
    (from order in orders
    from orderLine in order.orderLines
    group orderLine by orderLine.itemName into orderLineGrouping
    let totalQuantity = orderLineGrouping.Sum(ol => ol.quantity)
    select new { itemName = orderLineGrouping.Key, metric = totalQuantity }).ToList();

results.ForEach(resultItem => Console.WriteLine("{0} {1}", resultItem.itemName, resultItem.metric);

Answer 2

展平OrderLines

你需要让自己熟悉Enumerable.SelectMany这是

最有用的方法之一

来自LINQ的
SelectMany 将许多元素折叠为一个元素采集。生成的集合是另一种元素类型。我们指定元素如何转换为其他元素的集合元件。

var summary = orders.Where(x => x.OrderLines != null) // Check for null as there seems to be null orderlines in your model
                    .SelectMany(x => x.OrderLines)  // Flatten
                    .GroupBy(x => x.itemName)       // Group
                    .Select(group => new            // Project
                              {
                                 ItemName = group.Key,
                                 TotalQuantity = group.Sum(x => x.quantity)
                              })
                    .ToList();                      // To List

提示 ：为itemName和quantity

使用适当的大小写

Capitalization Conventions

下表总结了资本化规则标识符并提供不同类型的示例标识符

抱歉我的OCD刚刚开始

Answer 3

扁平化订单
将输出字符串的项目名称和数量分组
使用分组键和分组数量之和

参见代码：

var output = orders.SelectMany(x => x.orderLines)
    .GroupBy(x => x.itemName, x => x.quantity)
    .Select(x => $"{x.Key} : quantity = {x.Sum(y => y)}");

GroupBy项目和项目总和数量

3 个答案: