C# 复杂Linq c查询

我在林帕德试过这个

我有以下数据和linq查询，它应该只返回1条记录和2个图像，但返回2条记录和4个图像

我知道我有点不对劲，但不知道是什么。我正在寻找用户详细信息+汽车详细信息+用户的图像：0b3c2ba5-1538-4557-a6c0-7de701fd83e7

这与出价有关，因为当我删除用户0b3c2ba5-1538-4557-a6c0-7de701fd83e7的一个出价时，我会得到1条记录和2张图像

桌子 ---

投标表格 表用户详细信息 餐车 表2:U图像 质疑 ---

我正在寻找用户详细信息+汽车详细信息+用户图片： 0b3c2ba5-1538-4557-a6c0-7de701fd83e7

根据您在那一行中所说的判断，您可以通过将查询拆分为3个单独的查询并对汽车ID使用不同的函数来实现目标

行动方针如下：

从当前用户的bid表中查找所有不同的车辆ID 查找与步骤1中的数据对应的所有图像和用户/车辆详细信息 代码如下所示：

var carIDs=投标。其中x=>x.usedid==new Guid0b3c2ba5-1538-4557-a6c0-7de701fd83e7。选择x=>x.cardid.Distinct

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然后，您可以在两个单独的查询中选择用户详细信息和图像。

这是一个非常大的家庭作业。给你

使用此查询

            var query = from bd in lstbids
                    group bd by new { carid = bd.carid, userid = bd.userid } into gbd
                    join ud in lstuserdetails on gbd.First().userid equals ud.userid
                    join c in lstcars on gbd.First().carid equals c.id
                    where c.enabled && ud.userid == new Guid("0b3c2ba5-1538-4557-a6c0-7de701fd83e7")
                    select new
                    {
                        images = lstaction_images.Where(ai => ai.belongs_to == c.id),
                        bidamount = lstbids.Where(b => b.carid == c.id).OrderByDescending(b => b.id).Select(b => b.bidamount).DefaultIfEmpty(0).FirstOrDefault(),
                        ud.city,
                        ud.state,
                        c.name,
                        c.descr,
                        c.id,
                        c.listingOption,
                        c.priceStarting,
                        c.priceReserve,
                        gbd.FirstOrDefault().userid
                    };

注意：这个查询可以用更好的方式编写

以下是我认为您的表格是我的列表的示例表格：

表格/班级

数据/记录

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…你也没有投任何票。。。曾经。@spender他必须先有15个以上的代表。。。我同意他必须在他之前的问题中选择一些答案。@user389391:因为你在cars表上有两个元素，所以你要做两次select new{…}。@steve，是的，对此我深表歉意，但我确实记得，我收到的几乎所有建议都是错误的或没有帮助的：-也许我应该对此发表评论，但我的时间太忙了，以至于我经常继续下去，并找到另一种方法。我的目标是纠正我的标记：-@Tom我不确定我是否会这样做，因为我的目的是只找到一个用户的出价，并返回详细信息和最后一个用户的出价bid@user389391尝试此查询。。它适合你。请让我知道。再次感谢您为解决此问题所做的非常有趣的尝试，但是。。。结果返回用户0b3c2ba5-1538-4557-a6c0-7de701fd83e7的两个unqiue出价，当他们应该只有一个唯一的出价时，如数据所示。确定放弃我的上述评论，因为进一步的测试显示，你可能已经放弃了它，除非它得到一个错误：不支持的重载用于查询运算符“DefaultIfEmpty”。如果我把它拿出来，它似乎会起作用。进一步测试并将更新youThanks如果Prasads解决方案不起作用，我将尝试您的方法，因为我碰巧看到了他的解决方案，并首先尝试它，因为它位于顶部，并且更符合我希望的多功能一体查询：-

userid                                  city    state  
0b3c2ba5-1538-4557-a6c0-7de701fd83e7    Sydney  NSW  

id  name     descr   listingOption priceStarting priceReserve  
83  Valiant  Old Car     2              1000         1500  
86  Volvo    Safe Car    3              3000         4500 

id         image                                              belongs_to  
71  images/a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc/alpaca.JPG  83  
72  images/a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc/a_bag.jpg   83  
75  images/a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc/alpaca.JPG  86  
76  images/a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc/a_bag.jpg   86  

 var query = (from c in cars
                         from ud in users_details
                         from bd in bids
                         orderby c.listingOption descending
                         where a.userID == ud.userid
                        && c.id == bd.carID
                        && c.enabled == true
                        && bd.userID == new Guid("0b3c2ba5-1538-4557-a6c0-7de701fd83e7")
                         let images = from ai in auction_images
                                      where ai.belongs_to == c.id
                                      select ai

                         let bid = (from b in bids
                                    orderby b.id descending
                                    where b.carID == c.id
                                    select b.bidamount).FirstOrDefault()
                         select
                         new
                         {
                             images,
                             bidamount = (bid != null ? bid : 0),
                             ud.city,
                             ud.state,
                             c.name,
                             c.descr,
                             c.id,
                             c.listingOption,
                             c.priceStarting,
                             c.priceReserve,
                             bd.userID
                         }
                         );

query.Distinct().Dump();

            var query = from bd in lstbids
                    group bd by new { carid = bd.carid, userid = bd.userid } into gbd
                    join ud in lstuserdetails on gbd.First().userid equals ud.userid
                    join c in lstcars on gbd.First().carid equals c.id
                    where c.enabled && ud.userid == new Guid("0b3c2ba5-1538-4557-a6c0-7de701fd83e7")
                    select new
                    {
                        images = lstaction_images.Where(ai => ai.belongs_to == c.id),
                        bidamount = lstbids.Where(b => b.carid == c.id).OrderByDescending(b => b.id).Select(b => b.bidamount).DefaultIfEmpty(0).FirstOrDefault(),
                        ud.city,
                        ud.state,
                        c.name,
                        c.descr,
                        c.id,
                        c.listingOption,
                        c.priceStarting,
                        c.priceReserve,
                        gbd.FirstOrDefault().userid
                    };

public class userdetails
{ 
    public Guid userid { get; set; }
    public string city { get; set; }
    public string state { get; set; }
}

public class bids
{
    public int id { get; set; }
    public int carid { get; set; }
    public int bidamount { get; set; }
    public DateTime dateplaced { get; set; }
    public Guid userid { get; set; }
}

public class  cars
{
    public int id { get; set; }
    public string name { get; set; }
    public string descr { get; set; }
    public int listingOption { get; set; }
    public int priceStarting { get; set; }
    public int priceReserve { get; set; }
    public bool enabled { get; set; }
}

public class action_images
{
    public int id { get; set; }
    public string image { get; set; }
    public int belongs_to { get; set; }
}

        List<bids> lstbids = new List<bids>
        { 
            new bids {id= 43, carid=83, bidamount=625, dateplaced=Convert.ToDateTime("2012-11-05 16:12:51.600"), userid=new Guid("a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc") }, 
            new bids {id= 44, carid=86, bidamount=575, dateplaced=Convert.ToDateTime("2012-11-05 16:15:02.257"), userid=new Guid("a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc")  },
            new bids {id= 45, carid=83, bidamount=650, dateplaced=Convert.ToDateTime("2012-11-05 16:15:07.283"), userid=new Guid("a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc")  },
            new bids {id= 46, carid=86, bidamount=600, dateplaced=Convert.ToDateTime("2012-11-05 17:45:04.140"), userid=new Guid("a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc")  },
            new bids {id= 47, carid=86, bidamount=625, dateplaced=Convert.ToDateTime("2012-11-05 17:45:08.867"), userid=new Guid("a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc")  },
            new bids {id= 49, carid=83, bidamount=750, dateplaced=Convert.ToDateTime("2012-11-07 13:40:37.590"), userid=new Guid("0b3c2ba5-1538-4557-a6c0-7de701fd83e7")  },
            new bids {id= 52, carid=83, bidamount=850, dateplaced=Convert.ToDateTime("2012-11-08 13:40:37.590"), userid=new Guid("0b3c2ba5-1538-4557-a6c0-7de701fd83e7") },
        };

        List<userdetails> lstuserdetails = new List<userdetails>
        {
            new userdetails { userid = new Guid ("0b3c2ba5-1538-4557-a6c0-7de701fd83e7"), city = "Sydney", state = "NSW"},
        };

        List<cars> lstcars = new List<cars>
        {
            new cars {id = 83, name = "Valiant", descr = "Old Car", listingOption = 2, priceStarting = 1000, priceReserve = 1500, enabled = true },
            new cars {id = 86, name = "Volvo", descr = "Safe Car", listingOption = 3, priceStarting = 3000, priceReserve = 4500, enabled = true },
        };

        List<action_images> lstaction_images = new List<action_images>
        {
            new action_images { id = 71 , image = "images/a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc/alpaca.JPG", belongs_to =83 },
            new action_images { id = 72 , image = "images/a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc/a_bag.jpg", belongs_to =83 },
            new action_images { id = 75 , image = "images/a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc/alpaca.JPG", belongs_to =86 },
            new action_images { id = 76 , image = "images/a5d383e0-0c2c-44cf-9da1-0ce364b1dbdc/a_bag.jpg", belongs_to =86 },
        };