使用linq执行求和子查询

Question

请有人协助下面的查询。我试图选择每个客户端的所有收据总和。但是，我的select部分中的'Total ='子查询不起作用，并且出现以下错误：

无法创建类型为'AppName.Domain.Entities.AccountingEntry'的常量值。只有原始类型或枚举类型在此上下文中受支持。

我已经尝试过在查询后做一个ToList（），但这会导致同样的问题。使用linq选择Sum作为子查询的标准方法是什么？

var receipts = (from ae in repo.AccountingEntries 
         join c in repo.Clients on ae.ClientId equals c.ClientId 
         join m in repo.Memberships on c.MembershipId equals m.MembershipId 

         where 
          (ae.EntryDate <= start) && 
          (ae.ClientId != null) && 
          (ae.AccountingEntryTypeId == (byte)Shared.AccountingEntryTypes.Receipt) 


         select new AppName.Reports.Clients.AgeAnalysis.Receipt 
         { 
          ClientId = (Guid)ae.ClientId, 
          Client = c.FirstName + " " + c.LastName, 
          Membership = c.Membership.Name, 
          Total = (from ae2 in repo.AccountingEntries where ae2.ClientId == ae.ClientId select ae2.Total).Sum() 
         }); 

感谢， 加里

Answer 1

这似乎过于复杂和不必要的。如果您的实体模型设置正确，则可以通过删除连接并使用“group by”子句进行简化。沿线的东西：

from ae in c.AccountingEntries  
where 
    (ae.EntryDate <= start) && 
    (ae.ClientId != null) && 
    (ae.AccountingEntryTypeId == (byte)Shared.AccountEntyrTypes.Receipt) 
group by 
    ae.Client into g 
select 
    new AppName.Reports.Clients.AgeAnalysis.Receipt 
    { 
     ClientId = (Guid)g.Key.ClientId, 
     Client = g.Key.FirstName + " " + g.Key.LastName, 
     Membership = g.Key.Membership.Name, 
     Total = g.Sum(p => p.Total) 
    }