LINQ to XML选择与SQL IN子句类似的元素

Question

我有一些XML包含付款信息，包括付款正在应用的发票的详细信息。我想使用LINQ to XML来仅收集应用于某些发票（111,222,333）的付款。如果它是SQL我可以使用IN（111,222,333）关键字，但我不知道如何在LINQ中做同样的事情。

<Payment>
    <PaymentId>1</PaymentId>
    <Total>50</Total>
    <Invoice>
        <Id>111</Id>
        <Amount>20</Amount>
    </Invoice>
    <Invoice>
        <Id>555</Id>
        <Amount>30</Amount>
    </Invoice>
</Payment>
<Payment>
    <PaymentId>2</PaymentId>
    <Total>20</Total>
    <Invoice>
        <Id>222</Id>
        <Amount>20</Amount>
    </Invoice>
</Payment>
<Payment>
    <PaymentId>3</PaymentId>
    <Total>80</Total>
    <Invoice>
        <Id>888</Id>
        <Amount>80</Amount>
    </Invoice>
</Payment>

LINQ

var result = xml.Select(x => x.Element("Payment"))
               Where(x => x.Element("Id").Value.Contains("111","222","333"))

在此示例中，我想选择“PaymentId 1”和“PaymentId 2”，因为它们适用于ID为111,222或333的发票。

Answer 1

你可以对这些众所周知的Id列表进行匹配/交叉。

List<string> ids = new List<string> { "111", "222", "333" };

var result = xml
    .Elements("Payment")
    .Where(p => {
        var invoiceIds = p.Elements("Invoice").Elements("Id").Select(o => o.Value);
        return ids.Intersect(invoiceIds).Any();
    }
);

完整代码和NetFiddle。

---

const string XML = @"
    <root>
        <Payment>
            <PaymentId>1</PaymentId>
            <Total>50</Total>        
            <Invoice>
                <Id>555</Id>
                <Amount>30</Amount>
            </Invoice>
            <Invoice>
                <Id>111</Id>
                <Amount>30</Amount>
            </Invoice>
        </Payment>
        <Payment>
            <PaymentId>2</PaymentId>
            <Total>20</Total>
            <Invoice>
                <Id>222</Id>
                <Amount>20</Amount>
            </Invoice>
        </Payment>
        <Payment>
            <PaymentId>3</PaymentId>
            <Total>80</Total>
            <Invoice>
                <Id>888</Id>
                <Amount>80</Amount>
            </Invoice>
        </Payment>
    </root>
    ";

XElement xml = XElement.Parse(XML);
List<string> ids = new List<string> { "111", "222", "333" };

var result = xml
    .Elements("Payment")
    .Where(p => {
        var invoiceIds = p.Elements("Invoice").Elements("Id").Select(o => o.Value);
        return ids.Intersect(invoiceIds).Any();
        }
    );

foreach (var item in result)
{
    Console.WriteLine("PaymentId: {0}", (string)item.Element("PaymentId"));
}