复杂的 LINQ-TO-SQL 解决方案......或者只是我的经验不足？

Question

学习 LINQ-TO-SQL 并且进展顺利。但现在我认为我处于 "walk before you run" 阶段。

这个 LINQ-TO-SQL 有效：

var arr = (from up in db.fad_user_physician
           join u in db.fad_user on up.userID equals u.userID
           where up.physicianID.ToString() == userIdString
           select new ListOfUsersForPhysician
           {
               userID = u.userID,
               forename = u.forename,
               surname = u.surname,
               email = u.email,
               gender = u.gender,
               dobStr = u.dob.ToString()
           }).ToList();

我现在想在其中加入一个计算。因此 TSQL （有效）是：

（注意：physicianID 是我唯一需要使用的东西，从他们的登录详细信息中获得）

2016 年 2 月 17 日编辑16:03：

select fuf.userid,
    ((CAST(COUNT(fuf.userid)AS DECIMAL(6,2))/
    (DATEDIFF(dd,fu.dateJoined,GETDATE())*5))*100) AS 'percent'
from fad_user_physician fup
inner join fad_user fu on fu.userID = fup.userID
inner join fad_userFoods fuf on fuf.userID = fu.userID
inner join fad_food ff on ff.foodID = fuf.FoodID
where fup.physicianID = '5C46F531-FF64-4254-8072-F291627ABD3D'
AND fuf.quantityAmount >= ff.portionSize
group by fuf.userID,fu.dateJoined

所以基本上我想要一个医生的用户列表，以及百分比计算。

我在谷歌上搜索了很多小时，包括教程和所有内容。但只是陷入了 LINQ-TO-SQL 的复杂性（对于新手！）

我应该使用 LET 语句吗？我应该在 select 部分使用 LINQ-TO-SQL 语句吗？我试过了：

let maxPos = DbFunctions.DiffDays(u.dateJoined, DateTime.Now)*5
let temp = (from fuf in db.fad_userFoods 
            join ff in db.fad_food on fuf.foodID equals ff.foodID 
            join fu in db.fad_user on fuf.userID equals fu.userID 
            where fuf.userID.ToString() == userIdString 
                  && fuf.quantityAmount >= ff.portionSize 
            group fuf by new {num = fuf.userID} into e 
            select new {total = e.Key.num}).Count()

maxpos 给了我正确的值。但是 temp 给了我 0.

如有任何指导，我们将不胜感激！提前致谢。

Answer 1

您应该能够使用导航属性执行以下操作

var results = from fu in db.fad_user
              from fuf in fu.fad_userFoods
              from ff in fuf.fad_foods
              where fuf.userId = someGuid && fuf.quantityAmount >= ff.portionSize
              group fu.userid by new {fuf.userID, fu.dateJoined} into g
              select new 
              {
                  g.Key.userid,
                  Percent = 100 * ((decimal)(g.Count()) 
                            / (DbFunctions.DiffDays(g.Key.dateJoined, DateTime.Now) * 5))
              };

或者如果您没有导航属性，则使用 join

var results = from fu in db.fad_user 
              join fuf in db.fad_userFoods on fuf.userID equals fu.userID 
              join ff in db.fad_food on fuf.foodID equals ff.foodID 
              where fuf.userId = someGuid && fuf.quantityAmount >= ff.portionSize
              group fu.userid by new {fuf.userID, fu.dateJoined} into g
              select new 
              {
                  g.Key.userid,
                  Percent = 100 * ((decimal)(g.Count())
                            / (DbFunctions.DiffDays(g.Key.dateJoined, DateTime.Now) * 5))
              };

复杂的 LINQ-TO-SQL 解决方案......或者只是我的经验不足？

Complex LINQ-TO-SQL solution.......or just my inexperience?

c#

tsql

linq

linq-to-sql