获取分组 Linq 之外的参数

Question

例如，我需要使用 linq 从组中获取一些字段，这是我的代码：

(from PaymentTypes in PaymentTypes_DataTable.AsEnumerable()
join CashTransactions in CashTransactions_DataTable.AsEnumerable()
    on PaymentTypes.Field<Int32>("cashpaymenttype_id")
    equals CashTransactions.Field<Int32>("cashpaymenttype_id")
    into JoinedCashTransactions
from CashTransactions in JoinedCashTransactions.DefaultIfEmpty()
group CashTransactions by PaymentTypes.Field<Int32>("cashpaymenttype_id")
into GroupPaymentTypes
select new
{
    cashpaymenttype_id = 0, // Get PaymentTypeID
    cashpaymenttype_name = "", // Get PaymentTypeName
    cashtransaction_amount = GroupPaymentTypes.Sum(a =>
       a != null
          ? (a.Field<Int32>("cashtransactionstatus_id") == 1 ||
            a.Field<Int32>("cashtransactionstatus_id") == 3 ? 1 : -1) *
            a.Field<Double>("cashtransaction_amount") 
          : 0.00),
}).Aggregate(PaymentTypesTransactions_DataTable, (dt, result) => { 
    dt.Rows.Add(result.cashpaymenttype_id, result.cashpaymenttype_name,
   result.cashtransaction_amount); return dt; });

这个 linq 有效，但我需要cashpaymenttype_id字段并cashpaymenttype_name它们是否在PaymentTypes

Answer 1

假设 PaymentTypeID - PaymentTypeName 是 1 对 1，您可以将您的组更改为：

group CashTransactions by new 
{ 
    PaymentTypeId = PaymentTypes.Field<Int32>("cashpaymenttype_id"),
    PaymentTypeName = PaymentTypes.Field<String>("cashpaymenttype_name")
}
into GroupPaymentTypes

您的选择将如下所示：

select new
{
    cashpaymenttype_id = GroupPaymentTypes.Key.PaymentTypeId, 
    cashpaymenttype_name = GroupPaymentTypes.Key.PaymentTypeName, 
    ...
}