c# - LINQ:如何选择子节点满足条件的item元素？

Question

我的 XML 看起来像这样:

 <order>
    <order_number>1N</order_number>
    <execution_data>
        <exe_date>11/01/2011</exe_date>
        <exe_name>Joe</exe_name>
    </execution_data>
    <execution_data>
        <exe_date>12/01/2011</exe_date>
        <exe_name>Mike</exe_name>
    </execution_data>
    <execution_data>
        <exe_date>8/01/2011</exe_date>
        <exe_name>Steve</exe_name>
    </execution_data>
</order>
<order>
    <order_number>2N</order_number>
    <execution_data>
        <exe_date>11/01/2011</exe_date>
        <exe_name>Rob</exe_name>
    </execution_data>
    <execution_data>
        <exe_date>12/01/2011</exe_date>
        <exe_name>Marko</exe_name>
    </execution_data>
    <execution_data>
        <exe_date>8/01/2011</exe_date>
        <exe_name>Sam</exe_name>
    </execution_data>
</order>
<order>
    <order_number>3N</order_number>
    <execution_data>
        <exe_date>11/01/2011</exe_date>
        <exe_name>Nick</exe_name>
    </execution_data>
    <execution_data>
        <exe_date>12/01/2011</exe_date>
        <exe_name>Ashley</exe_name>
    </execution_data>
    <execution_data>
        <exe_date>8/01/2011</exe_date>
        <exe_name>Marc</exe_name>
    </execution_data>
</order>


    public class ExecutionItem
    {
       public string Date {get;set;}
       public string Name {get;set;}
    }

    public class Response
    {
       public List<ExecutionItem> ExecutionItems{get;set;}
    }

如何选择 order_number 等于 1N 的订单，然后使用 LINQ 从该订单中获取所有 execution_data？

Answer 1

嗯，这里有两种方法:

• 你可以找到所有 <order_number>值为 1N 的元素，然后找到所有兄弟 execution_data元素
• 你可以找到order具有相关元素的 order_number元素，然后找到 child execution_data元素。

我可能会选择后一种方法，类似于:

var executionDataElements = 
      doc.Descendants("order")
         .Where(order => (string) order.Element("order_number") == "1N")
         .SelectMany(order => order.Elements("execution_data");

(请注意，如果这匹配了多个订单，您将从所有匹配订单中获取所有元素。)

第一种方法如果您知道 execution_data元素在 order_number 之后元素，如果你知道只有一个这样的 order_number元素，将是:

var executionDataElements = doc.Descendants("order_number")
                               .First(x => (string) x == "1N")
                               .ElementsAfterSelf("execution_data");