LINQ 等效于 WHERE IN 子句

Question

我有 3 个表 Purchase、PurchaseBill 和 PurchasePayment。

Purchase 与 PurchaseBill
是一对多关系 PurchaseBill 与 PurchasePayment

是一对多关系

我正在寻找与此 SQL 查询

等效的 Linq（流畅）

SELECT COUNT('') FROM PurchasePayment
WHERE PurchaseBillId IN (
   SELECT PurchaseBillId FROM PurchaseBill WHERE PurchaseId = @PurchaseId
)

基本上我想知道某些 @PurchaseId

是否存在任何 PurchasePayment 记录

目前我正在使用

                var bills = _context.PurchaseBill.Where(a => a.PurchaseId == obj.Id);

                foreach (var bill in bills)
                {
                    var hasPayment = _context.PurchasePayment.Any(a => a.PurchaseBillId == bill.Id);

                    if (hasPayment)
                        ctx.AddFailure("Cannot modify paid Purchase.");
                }

我试过了
var hasPayment = _context.PurchasePayment.Any(w => bills.Contains(w.PurchaseBillId));
但它不工作。是否可以在 Linq 中不循环执行？

Answer 1

你可以这样实现：

var PurchaseId=1;
var result = _context.PurchasePayment.Where(x=>_context.PurchaseBill.Where(y=>y.PurchaseId==PurchaseId).Select(y=>y.PurchaseBillId).ToList().Contains(x.PurchaseBillId)).Count();

Answer 2

你试过这个吗：

var hasPayment = _context.PurchasePayment.Where(x => _context.PurchaseBill.Where(a => a.PurchaseId == obj.Id).Any(y => y.PurchaseBillId == x.PurchaseBillId)).Any();

我在这里试了一个例子： https://dotnetfiddle.net/uTs6pd

Answer 3

我同意格特的观点；你应该有一个 PurchaseBill class 和一个 ICollection<PurchasePayment> PurchasePayments 属性（链接到多笔付款）和一个 int PurchaseId 属性（链接回单次购买）并能够执行以下操作：

var hasPayment = context.PurchaseBills.Any(
  pb => pb.PurchaseId == obj.Id && pb.PurchasePayments.Any()
);

“是否有带有 PurchaseId blahblah 和任何 PurchasePayment 的采购单？”

或者，如果您打算对每张账单及其付款进行处理，例如：

var bills = context.PurchaseBills.Include(pb => pb.PurchasePayments);

foreach(var pb in bills){

  if(pb.PurchasePayments.Any()){
    //do something with the bill and its purchase here
  }
}

但是如果您要做的只是向错误列表添加一条消息，请不要这样做；为了查看并找到一个可能有付款记录的账单记录，需要下载大量数据——最好通过第一个建议来完成，该建议要求数据库提供一个简单的布尔值——“是否有任何地方为此付款purchaseId?"

LINQ 等效于 WHERE IN 子句

LINQ equivalent of WHERE IN clause

c#

sql

linq

entity-framework