Question

请有人协助以下查询。我正在尝试为每个客户选择所有收据的总和。但是我的选择部分中的'Total ='子查询无效，我收到以下错误：

无法创建“AppName.Domain.Entities.AccountingEntry”类型的常量值。在此上下文中仅支持原始类型或枚举类型。

我已经尝试在该查询之后执行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()
                        });

谢谢，加里

Answer 1

这似乎过于复杂和不必要。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”子句来简化。有点像：

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 )
    }

使用linq执行求和子查询

1 个答案: