groupby 后字段不可见？

Question

我现在拥有的：

var batch_pymnts2 = (from a in ctx.WarehouseStatementBatchPayments
                     join b in ctx.WarehouseStatementBatches on a.WarehouseStatementBatchID equals b.ID
                     join c in ctx.WarehousePaymentInvoices on a.ID equals c.WarehouseStatementBatchPaymentID
                     where b.ID == batchID
                     select new
                     { 
                         PaymentId = a.ID, 
                         PaymentNet = a.Net, 
                         PaymentType = a.Type 
                     })
                     .GroupBy(d => d.PaymentId).Where(x => x.Count() == 1);

我需要像这样查询这些结果：

var test = (from a in batch_pymnts2 where a.PaymentNet > 100 select a).ToList();

但是，我看不到第一条语句用于将结果投影到的（匿名）类型的字段。

我需要在查询中使用定义的类型来进行投影吗？有没有办法用匿名类型做到这一点？

[更新]
我设法稍微更改了源查询，将 group by 移动到 group by 内部和之前。这使得被投影的匿名类型的字段在进一步的语句中被“公开”。

            var count2 =  (from a in WarehouseStatementBatchPayments
                                                 join b in WarehouseStatementBatches on a.WarehouseStatementBatchID equals b.ID
                                                 join c in WarehousePaymentInvoices on a.ID equals c.WarehouseStatementBatchPaymentID
                                                 group a by a.ID into grp
                                                 from d in grp
                                                 where d.WarehouseStatementBatchID == batchID && grp.Count() == 1
                                                 select new { PaymentId = d.ID, PaymentNet = d.Net, PaymentType = d.Type }).ToList();   

Answer 1

batch_pymnts2 是一组对象的序列。实际上，它是您的匿名类型的集合的集合。 batch_pymnts2 中的每个项目都有这个：

group.Key; /* a PaymentId value */

((IEnumerable)group); /* the anon type items grouped together in this group */

Those group objects implement the IGrouping interface。他们的Key 属性是定义组的PaymentId 值。如果您枚举组（它们实现IEnumerable<T>），您将获得按PaymentId 分组的匿名对象：

var test = batch_pymnts2.SelectMany(g => g.Where(anon => anon.PaymentNet > 100));

test 现在是您的匿名类型的枚举，因为我们现在已经枚举了来自每个组的 anon 项目的子集，并且（实际上）将所有这些小的 anon 枚举合并为一个大的枚举。

如果您想选择至少有一个匿名事物且 PaymentNet > 100 的群组，请尝试以下操作：

//  Groups which have at least one PaymentNet > 100
var t2 = batch_pymnts2.Where(g => g.Any(anon => anon.PaymentNet > 100));

//  PaymentIds of the groups which have at least one PaymentNet > 100
var ids = t2.Select(g => g.Key);

//  PaymentIds that appear only once
var singles = t2.Where(g => g.Count == 1).Select(g => g.Key);

我不知道您为什么要对它们进行分组，或者您的 PaymentNet > 100 查询要完成什么，所以我不确定如何编写您想要的查询。但是您的出发点是您要查询包含匿名类型枚举的 group 对象序列，而不是该类型本身的序列。