如何将 SQL 命令转换为实体框架和 Lambda 表达式

Question

我想将一些 SQL 代码转换为实体框架

select *
into #invoice
from Invoice
where Track = 2

select Fuel.ID, SUM(ISNULL(#invoice.Price, 0)) as Price, SUM(ISNULL(#invoice.Price, 0))
from Fuel left outer join #invoice
on Fuel.ID = #invoice.Fuel
group by Fuel.ID

尝试编写此代码但结果为零 (0)（价格和升）

var data = fules.GroupJoin(model,
          f => f.ID,
          m => m.ID,
           (f, m) => new { f, m })
         .SelectMany(x => x.m.DefaultIfEmpty(),
         (x, m) => new { Fuel = x.f, Price = m?.Price, Liter = m?.Liter })
          .GroupBy(A => A.Fuel)
          .Select(A => new { Fuel = A.Key.Name, Liter = A.Sum(B => B.Liter)
, Price = A.Sum(B => B.Price) })
              .ToList();

Answer 1

您不会将 SQL 转换为这样的 LINQ/Lambda 函数。而是从结果“grain”开始，然后按照导航属性填写投影列。

类似：

db.Feuls.Select( f => new 
   {
      Fuel = f.Name, 
      Liter = f.Invoices.Where( i => i.Track = 2 ).Sum( i => i.Liter ),
      Price = f.Invoices.Where( i => i.Track = 2 ).Sum( i => i.Price )
   });

Answer 2

我认为您正在寻找这样的东西：

var query = from f in db.Feuls
            from i in f.Invoices.Where(x => x.Track == 2).DefaultIfEmpty()
            group i by f.ID into g
            select new
            {
               ID = g.Key,
               Liter = g.Sum(x => g.Liter),
               Price = g.Sum(x => g.Price)
            };