我正在使用 asp.net MVC，试图制作一个表格来显示品牌在几天内每天的总利润，并且我正在努力解决如何包含品牌净利润为 0 的日子。在我查询商店在给定时间范围内的购买总数后，在名为purchaseQuery的变量中，它为我提供了品牌名称、购买日期（作为整数）、该商品的价格以及该商品的数量在那次交易中购买的。假设每个品牌只销售一种产品，并且该产品的价格每天都会波动。该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 purchasedelse{ 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 });}我想要进行转换，以便 BrandsProfit 具有名称、日期列表以及与每一天相对应的每日利润列表。这样，商品列表中的每个商品都将具有唯一的品牌名称，因为它将适用于每次购买，而不是仅适用于购买该品牌商品的日期。我觉得我把事情变得过于复杂了，我主要担心的是，如果一个品牌一天有 0 次购买，我可能会得到一个大小为 5 的天数列表，以及一个大小为 的购买列表4、我需要它们的尺寸相同。感谢您的帮助，并感谢您花时间阅读我的问题。
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绝地无双
TA贡献1946条经验 获得超4个赞
此类问题非常适合使用 LINQ。
下面的 LINQ 查询首先创建不同日期和品牌名称的外连接。这为我们提供了全天可以加入的所有品牌的列表。这样，每个品牌都会有相同的天数，即使它在某一天从未售出任何商品。
然后，它会根据该品牌/日期列表加入购买，如果当天没有记录该品牌的购买，则会使用 来创建零成本/数量的替代购买DefaultIfEmpty。
然后，该连接的结果将被投影到对象列表中BrandsProfit。
例如，如果某一天没有购买某个品牌，您会注意到在示例数据列表中，“2”天的品牌“B”被注释掉了；但在结果中，“2”天仍然存在品牌“B”的行，每日总利润为零。
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，您可以考虑更新用于生成数据的源查询，以purchaseQuery使用像上面这样的外连接...这样您就会有一个行代表品牌/天的每个组合，即使某个品牌从未在特定日期销售过。
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