Linq to Entities 中的左外连接 (asp.net vb)

Question

我被这个问题困扰太久了，我认为这只是我的经验不足。我研究过许多类似的文章，但 none 似乎在我将其应用于我的情况时起作用。

我正在使用 linq to entities with EF6.I 有两个简单的 tables 'LoanRepayment' 和 'LoanReceipt'。他们与从 LoanRepayment.LoanPaymentId 到 LoanReceipt.LoanPaymentId 的外国有联系。有 48 个固定贷款付款，其中 4 个有收据。我只是想创建一个包含 48 行的 table，其中包含来自 LoanRepayment table 的所有 48 行和任何存在的收据数据（即 4）。尚未支付的贷款旁边的其余单元格应为空白。

Dim queryLoanRepayments = (From lp In proxifundContext.LoanRepayments Group 
Join lr In proxifundContext.LoanReceipts On lr.LoanPaymentId Equals
lp.LoanPaymentId Into paymentlist = Group From lr In 
paymentlist.DefaultIfEmpty() Select lp.InstallmentNo, lp.InstallmentAmount, 
lp.Penalty, lp.PaymentDate, If(lr.ReceiptDate Is Nothing, String.Empty, 
lr.ReceiptDate), If(lr.Amount Is Nothing, String.Empty, lr.Amount)).ToList()

当我运行时，智能感知上面的查询用消息 "Range variable name can be inferred only from a simple or qualified name with no arguments".

在两个 If 语句下划线

我做错了什么？

Answer 1

您应该自己给计算出的属性命名，因为 VB 无法推断它们（就像从简单的属性中推断的那样）：

...
Select lp.InstallmentNo, 
       lp.InstallmentAmount, 
       lp.Penalty,
       lp.PaymentDate,
       ReceiptDate = If(lr.ReceiptDate Is Nothing, String.Empty, 
       lr.ReceiptDate),
       Amount = If(lr.Amount Is Nothing, String.Empty, lr.Amount)

Answer 2

谢谢格特·阿诺德。你给我指明了正确的方向。实际有效的声明是：

Dim queryLoanRepayments = (From lp In proxifundContext.LoanRepayments Group 
Join lr In proxifundContext.LoanReceipts On lr.LoanPaymentId Equals 
lp.LoanPaymentId Into paymentlist = Group From lr In 
paymentlist.DefaultIfEmpty() 
Select lp.LoanApplicationId, 
       lp.InstallmentNo, 
       lp.InstallmentAmount, 
       lp.Penalty, 
       lp.PaymentDate, 
       ReceiptDate = If(lr.ReceiptDate = Nothing, String.Empty, CStr(lr.ReceiptDate)), 
       Amount = If(lr.Amount = Nothing, String.Empty, CStr(lr.Amount))).ToList()

Linq to Entities 中的左外连接 (asp.net vb)

Left outer join in Linq to Entities (asp.net vb)

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linq-to-entities

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