Question

我有以下Linq-to-SQL查询。在第5行，我正在尝试从我的Packages表中获取记录的数量，其中满足我的Where语句中列出的条件。我认为除了第5行之外，这段代码中的一切都是正确的。我做错了什么？

var Overage = from s in db.Subscriptions
    join p in db.Packages on s.UserID equals p.UserID
    where 
      s.SubscriptionType != "PayAsYouGo" && 
      (s.CancelDate == null || s.CancelDate >= day) && 
      s.StartDate <= day && p.DateReceived <= day && 
      (p.DateShipped == null || p.DateShipped >= day)
    let AverageBoxSize = (p.Height * p.Length * p.Width) / 1728
    let ActiveBoxCount = p.Count()
    select new
    {
      p,
      AverageBoxSize,
      ActiveBoxCount,
      s.Boxes
    };

错误消息是“Foo.Data.Package的未知方法Count（）”

编辑以下是我的问题的示例：

订阅表：

UserID | Boxes
001      5
002      25
003      5

Boxes是每个用户在其订阅下被允许的最大数量

套餐表

UserID | PackageID | Height | Length | Width
001      00001       10       10       10
001      00002       10       10       10
001      00003       20       10       10
003      00004       10       20       20
003      00005       10       10       10

所需的查询结果

UserID | Boxes | Box Count | Average Box Size
001      5           3           1,333
003      5           2           2,500

用户002未出现，因为Where子句排除了该用户

Answer 1

P不是一个集合。它应该是：让ActiveBoxCount = db.Packages.Count（）

Answer 2

根据你对Ryan回答的评论，这可能是你想要的：

var Overage = from s in db.Subscriptions
    join p in db.Packages on s.UserID equals p.UserID
    where 
      s.SubscriptionType != "PayAsYouGo" && 
      (s.CancelDate == null || s.CancelDate >= day) && 
      s.StartDate <= day && p.DateReceived <= day && 
      (p.DateShipped == null || p.DateShipped >= day)
    select new
    {
      p,
      AverageBoxSize = (p.Height * p.Length * p.Width) / 1728,
      ActiveBoxCount = db.Packages.Where(x => x.UserID == p.UserID).Count(),
      s.Boxes
    }

Answer 3

最简单的方法是用 -

替换你的Let行

Group <columns> By UserId into summary = Group 
Aggregate x in summary Into ActiveBoxCount = x.Count

如何在Linq to Sql代码中修复此Count语句？

3 个答案: