Lambda表达式在C#中按分组

本文关键字：表达式 Lambda | 更新日期: 2023-09-27 18:21:09

我想按ItemNumber对我的LINQ查询进行分组，并返回整个表和Quantity的总数。

Example:
ItemNumber - ItemName - Quantity
100          Item1       1
150          Item2       2
100          Item1       2
200          Item3       1
150          Item2       2
Should be:
ItemNumber - ItemName - Quantity
100          Item1       3
150          Item2       4
200          Item3       1

这是我试图分组的查询：

public IQueryable<WebsiteOrderStatus> GetOrderStatusByAccountNumberWithoutDeleted
        (string accountNumber)
{
    return db.WebsiteOrderStatus
             .Where(x => x.AccountNumber == accountNumber && x.LastUpdatedStatus != 1);
}

到目前为止我最好的结果（虽然无法编译）：

public IQueryable<IGrouping<Int32?, WebsiteOrderStatus>> lol(string accountNumber)
{
     db.WebsiteOrderStatus
       .Where(x => x.AccountNumber == accountNumber && x.LastUpdatedStatus != 1)
       .GroupBy(g => g.ItemNumber)
       .Select(g => new
                    {
                         g.Key.ItemNumber,
                         Column1 = (Int32?)g.Sum(p => p.Quantity)
                    });
 }

编辑：

谢谢大家的回复，我必须面对。在我看来，这些匿名类型很难处理，所以我找到了另一个解决方案。

我做了另一种方法，对用户项目的数量进行求和，并对第一个项目进行分组。

public IQueryable<WebsiteOrderStatus> GetOrderStatusByAccountNumberWithoutDeleted(string accountNumber)
{
    return db.WebsiteOrderStatus.Where(x => x.AccountNumber == accountNumber && x.LastUpdatedStatus != 1).GroupBy(x => x.ItemNumber).Select(grp => grp.First());
}
public int GetQuantityOfUsersItem(string accountNumber, string itemNumber)
{
    return db.WebsiteOrderStatus.Where(x => x.ItemNumber == itemNumber && x.AccountNumber == accountNumber).Sum(x => x.Quantity);
}

在我有我的网格视图的页面上，我做了：

var query = websiteOrderStatusRep.GetOrderStatusByAccountNumberWithoutDeleted(AppSession.CurrentLoginTicket.AccountNumber).Select(x => new { x.ItemName, x.ItemNumber, x.FormatName, x.Price, x.Status, x.Levering, Quantity = websiteOrderStatusRep.GetQuantityOfUsersItem(x.AccountNumber, x.ItemNumber)});

Lambda表达式在C#中按分组

public IQueryable<IGrouping<Int32?, WebsiteOrderStatus>> lol(string accountNumber)
{
     db.WebsiteOrderStatus
       .Where(x => x.AccountNumber == accountNumber && x.LastUpdatedStatus != 1)
       .GroupBy(g => g.ItemNumber)
       .Select(g => new
                    {
                         ItemNumber = g.Key,
                         ItemName = g.First().ItemName,
                         Count = g.Sum(item => item.Quantity)
                    });
 }

 public IQueryable<OrderStatus > lol(string accountNumber)
 {
     return db.WebsiteOrderStatus
        .Where(x => x.AccountNumber == accountNumber && x.LastUpdatedStatus != 1)
        .GroupBy(g => g.ItemNumber)
        .Select(g => 
                new OrderStatus //This is your custom class, for binding only
                {
                     ItemNumber = g.Key,
                     ItemName = g.First().ItemName,
                     Quantity = g.Sum(g => g.Quantity)
                }
        );
 }

我认为Select应该是：

   .Select(g => new
                {
                     ItemNumber = g.Key,
                     Column1 = (Int32?)g.Sum(p => p.Quantity)
                });

请注意匿名类型第一行中的更改。分组的关键字已经是物料编号。

我在您的查询中看到的唯一问题是

  1. 根据注释缺少return语句
  2. select语句应为：

-

.Select(g => new {
       ItemNumber = g.Key,
       Total = g.Sum(p => p.Quantity)
    });

编辑：如果你想在结果对象中得到，比如ItemNumber和ItemName，你还必须在这些字段上分组

db.WebsiteOrderStatus
   .Where(x => x.AccountNumber == accountNumber && x.LastUpdatedStatus != 1)
   .GroupBy(g => new { g.ItemNumber, g.ItemName })
   .Select(g => new
                {
                     ItemNumber = g.Key.ItemNumber,
                     ItemName = g.Key.ItemName,
                     Count = g.Sum(item => item.Quantity)
                });

返回值类型不能使用匿名类型。所以你永远不会编译代码。

此外，您的linq表达式具有IQueryable<[匿名类型]>结果类型。

我相信你可以做这样的事情：

public IQueryable<OrderStatus> lol(string accountNumber) 
{ 
     db.WebsiteOrderStatus 
       .Where(order => order.AccountNumber == accountNumber && order.LastUpdatedStatus != 1) 
       .GroupBy(order => order.ItemNumber) 
       .Select(grouping => new OrderStatus //This is your custom class, for binding only
                    { 
                         ItemNumber = grouping.Key, 
                         ItemName = grouping.First().ItemName, 
                         Quantity = grouping.Sum(order => order.Quantity) 
                    }); 
}

我也修正了我的答案：）

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