C＃LINQ join - 在辅助连接中使用范围变量

Question

我正在尝试使用一些linq magic来查询两个不同的数据集，以比较一个数据集上的内部属性，以查看该值是否大于另一个数据集中的属性。我已经推广了类布局并删除了一些属性，希望能让它更清晰。

public class Contract
{
    public string ContractId { get; set; }
    public IList<Invoice> InvoiceList { get; set; }

    public class Invoice
    {
        public int InvoiceNumber { get; set; }
        public decimal CurrentDueAmount { get; set; }
    }
}

public class PaymentRequest
{
    public IList<ContractList> Contracts { get; set; }
    public class ContractList
    {       
        public string ContractId { get; set; }  
        public IList<InvoiceList> Invoices { get; set; }
    }

    public class InvoiceList
    {          
        public decimal CurrentDueAmount { get; set; }
    }
}

我知道以下LINQ语句不起作用，但它是关于我正在努力实现的一般想法。

from validContract in validContracts
join contract in paymentRequest.Contracts
on validContract.ContractId equals contract.ContractId

from validInvoice in validContract.InvoiceList
join invoice in contract.Invoices
on validInvoice.InvoiceNumber equals invoice.InvoiceNumber

where invoice.CurrentDueAmount > validInvoice.CurrentDueAmount
select "Invoice Number: " + invoice.InvoiceNumber + ", Current Due >= " + validInvoice.CurrentDueAmount;

尝试在第二个连接语句中使用范围变量“contract”时出错。

我希望能够对象currentDueAmounts进行比较。任何想法/重构，方法提取等将不胜感激。

Answer 1

您需要在加入它们之前将这两个集合分开，如此

var query =
    from valid in (
         from contract in validContracts
         from invoice in contract.InvoiceList
         select new { contract, invoice }
    )
    join request in (
        from contract in paymentRequest.Contracts
        from invoice in contract.Invoices
        select new { contract, invoice }
    )
    on new { valid.contract.ContractId, valid.invoice.InvoiceNumber }
    equals new { request.contract.ContractId, request.invoice.InvoiceNumber }
    where request.invoice.CurrentDueAmount > valid.invoice.CurrentDueAmount
    select "Invoice Number: " + request.invoice.InvoiceNumber + ", Current Due >= " + valid.invoice.CurrentDueAmount;