不确定如何正确地将数据提取到包含字符串、int和double属性的类的列表中

Question

我正在与asp.net MVC合作，试图制作一个表格来显示品牌每天在几天内的总利润，我正在努力解决如何将品牌净利润为0的天数包括在内。

当我在名为purchaseQuery的变量中查询商店在给定时间范围内的购买总数后，它将给我品牌名称、购买日期(作为一个整数)、该商品的价格以及在该交易中购买的商品的金额。假设每个品牌只销售一种产品，并且该产品的价格每天都在波动。此代码位于该查询之后。

purchasedItems = new List<BrandsTransactionItem>();

foreach (var query in purchaseQuery)
{
BrandsTransactionItem tempItem;
tempItem = purchasedItems.Where(e => e.day == query.day).Where(e => e.brandName == query.brandName).FirstOrDefault();

//If item not in list already, 
if (tempItem == null)
{
   purchasedItems.Add(new BrandsTransactionItem()
   {
    brandName = query.brandName,
    day = query.day,
    totalPurchased = query.TotalPurchased,
    costOfItem = query.costOfItem
   });
}
// if it already exists, just add to amount purchased
else
{
  tempItem.totalPurchased += query.totalPurchased;
}
}

foreach (var item in purchasedItems)
{
  double dailyProfit = (double)(item.totalPurchased * item.costOfItem);
  dailyProfit = Math.Round(dailyProfit, 2); // make it decimal of 2

  // Items is the list that I want to display in MVC
  Items.Add(new BrandsProfit(){
  brandName = item.brandName,
  day = item.day,
  totalDailyProfit = dailyProfit
  });
}

我想要转换，这样BrandsProfit就会有一个名称，一个日期列表，以及一个与这些日期对应的dailyProfits列表。这样，项目列表中的每个项目都将具有唯一的品牌名称，因为它将应用于每一次购买，而不是仅在购买品牌项目的天数内应用。

我觉得我已经把事情复杂化了，我主要担心的是，如果一个品牌一天有0个购买，我可能会有一个大小为5的天数列表和一个大小为4的购买列表，我需要它们的大小相同。

感谢您的帮助，感谢您抽出时间阅读我的问题。

Answer 1

这类问题是使用LINQ的一个很好的选择。

下面的LINQ查询首先创建不同日期和品牌名称的外连接。这给了我们一个列表，列出了我们可以加入的所有天的所有品牌。这样，每个品牌都将拥有相同的天数，即使它从未在特定的一天售出任何商品。

然后，它根据该品牌/天数列表加入购买，如果当天没有记录该品牌的购买，则使用DefaultIfEmpty创建零成本/数量的替代购买。

然后，该联接的结果被投影到BrandsProfit对象列表中。

例如，如果某个品牌在某一天没有购买，您会注意到，在样本数据列表中，"2“天的品牌"B”被注释掉了；但在结果中，"2“天的品牌"B”仍然有一行，TotalDailyProfit为0。

void Main()
{
    var purchases = new List<Purchase>() {
        new Purchase() { BrandName = "A", CostOfItem = 1.13M, Day = 1, TotalPurchased = 125 },
        new Purchase() { BrandName = "B", CostOfItem = 1.52M, Day = 1, TotalPurchased = 165 },
        new Purchase() { BrandName = "C", CostOfItem = 1.90M, Day = 1, TotalPurchased = 836 },
        new Purchase() { BrandName = "A", CostOfItem = 1.74M, Day = 2, TotalPurchased = 583 },
        //new Purchase() { BrandName = "B", CostOfItem = 1.52M, Day = 2, TotalPurchased = 785 },
        new Purchase() { BrandName = "C", CostOfItem = 1.42M, Day = 2, TotalPurchased = 369 },
        new Purchase() { BrandName = "A", CostOfItem = 1.93M, Day = 3, TotalPurchased = 789 },
        new Purchase() { BrandName = "B", CostOfItem = 1.87M, Day = 3, TotalPurchased = 739 },
        new Purchase() { BrandName = "C", CostOfItem = 1.78M, Day = 3, TotalPurchased = 436 },
    };

    var results = from day in purchases.Select(x => x.Day).Distinct()
                  from brand in purchases.Select(x => x.BrandName).Distinct()
                  join purchase in purchases on new { Brand = brand, Day = day } equals new { Brand = purchase.BrandName, Day = purchase.Day } into j
                  from result in j.DefaultIfEmpty(new Purchase() { BrandName = brand, Day = day, TotalPurchased = 0, CostOfItem = 0 })
                  select new BrandsProfit()
                  {
                      BrandName = result.BrandName,
                      Day = result.Day,
                      TotalDailyProfit = result.TotalPurchased * result.CostOfItem
                  };

    Debug.WriteLine(JsonConvert.SerializeObject(results, Newtonsoft.Json.Formatting.Indented));
}

class Purchase
{
    public string BrandName { get; set; }
    public int Day { get; set; }
    public int TotalPurchased { get; set; }
    public decimal CostOfItem { get; set; }
}

class BrandsProfit
{
    public string BrandName { get; set; }
    public int Day { get; set; }
    public decimal TotalDailyProfit { get; set; }
}

产生以下结果：-

[
  {
    "BrandName": "A",
    "Day": 1,
    "TotalDailyProfit": 141.25
  },
  {
    "BrandName": "B",
    "Day": 1,
    "TotalDailyProfit": 250.80
  },
  {
    "BrandName": "C",
    "Day": 1,
    "TotalDailyProfit": 1588.40
  },
  {
    "BrandName": "A",
    "Day": 2,
    "TotalDailyProfit": 1014.42
  },
  {
    "BrandName": "B",
    "Day": 2,
    "TotalDailyProfit": 0.0
  },
  {
    "BrandName": "C",
    "Day": 2,
    "TotalDailyProfit": 523.98
  },
  {
    "BrandName": "A",
    "Day": 3,
    "TotalDailyProfit": 1522.77
  },
  {
    "BrandName": "B",
    "Day": 3,
    "TotalDailyProfit": 1381.93
  },
  {
    "BrandName": "C",
    "Day": 3,
    "TotalDailyProfit": 776.08
  }
]

如果您不想继续使用上面的示例，可以考虑将用于在purchaseQuery中生成数据的源查询更新为使用类似上面的外连接...这样，即使某个品牌从未在特定的一天售出，您也会为每个品牌/天的组合安排一行。