Question

我有以下订单对象，其中包含订单插件列表。我正在尝试创建一个报告，显示所有插件类型及其数量总和。

public class Order {
     public IList<OrderAddon> OrderAddons { get; set; }
}

public class OrderAddon {
     public enum OrderType { get; set; }
     public string Name { get; set; }
     public int Quantity { get; set; }
}

这就是我所处的位置，无法弄清楚整个查询是否错误，我只是错过了什么。

var query = from order in Model.Orders
            from addon in order.OrderAddons
            group order by addon.AddonType
            into orderAddons select new
            {
                 Name = orderAddons.Key,
                 Quantity = orderAddons.Sum(x => x.) << This is where I am stuck
            };

当我击中时。我的intellisense在订单对象中显示属性而不是插件对象。

Answer 1

那是因为你说的是group order by ...，所以orderAddons对象变成了order的分组。如果你需要两个对象的属性，你可以使用它：

from order in Model.Orders
from addon in order.OrderAddons
group new{addon, order} by addon.AddonType
into orderAddons select new
{
    Name = orderAddons.Key,
    Quantity = orderAddons.Sum(x => x.addon.Quantity)
};

如果这是您需要的所有数据，这有点简单：

from order in Model.Orders
from addon in order.OrderAddons
group order.Quantity by addon.AddonType
into quantityByAddonType select new
{
    Name = quantityByAddonType.Key,
    Quantity = quantityByAddonType.Sum()
};

Answer 2

替代语法相同的结果...

var result = Model.Orders
  .SelectMany(order => order.OrderAddons)
  .GroupBy(addon => addon.OrderType)
  .Select(grouping => new
  {
      Name = grouping.Key,
      Quantity = grouping.Sum(addon => addon.Quantity)
  });

LINQ Sum列表中按类型分组的项目列表

2 个答案: