C# 基于属性查找XML元素

假设我有这个XML

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" mergefield="blah">

    <filter blah="rrr"></filter>
    <filter blah="qqq"></filter>
    <filter blah="www"></filter>

</hibernate-mapping>

}

问题

现在我遇到了一种情况，

mergefield

可以是

“blah”

或

“blahblah”

。因此，我希望上述代码以同样的方式用于此XML：

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" mergefield="blah,blahblah">

    <filter blah="rrr"></filter>
    <filter blahblah="qqq"></filter>
    <filter blahblah="www"></filter>

</hibernate-mapping>

我无法完成查询部分

XElement targetElement = target.Elements().SingleOrDefault(
                        t =>
                            String.Equals(
                                (string)t.Attribute(GetMergeAttr(target).SingleOrDefault(u=> ?????????)),
                                (string)sourceElement.Attribute(GetMergeAttr(source).SingleOrDefault(u => ?????????))
                                )
                      );

这是可行的，但是如果我有3个以上的mergefield值（我需要更新此查询以接受任意数量的mergefields，而不仅仅是2个）：

            XElement targetElement = target.Elements().SingleOrDefault(
                    t =>
                        String.Equals(
                            (string)t.Attribute(GetMergeAttr(target).Last())?? (string)t.Attribute(GetMergeAttr(target).First()),
                            (string)sourceElement.Attribute(GetMergeAttr(source).Last()) ?? (string)sourceElement.Attribute(GetMergeAttr(source).First())
                            )
                  );

---

我不确定您想要实现什么，但这段代码的行为是否符合预期

using System;
using System.Linq;
using System.Xml.Linq;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var path = (@"PATH");
            XElement target = XElement.Load(path);
            XElement source = XElement.Load(path);
            var mergefields = GetMergeAttr(target);

            foreach (var sourceElement in source.Elements())
            {
                var targetElements = from mergefield in mergefields
                                     select target.Elements().SingleOrDefault(t => 
                                         {
                                             if (t.Attribute(mergefield) == null || sourceElement.Attribute(mergefield) == null)
                                             {
                                                 return false;
                                             }

                                             return String.Equals(
                                             t.Attribute(mergefield).Value,
                                             sourceElement.Attribute(mergefield).Value,
                                             StringComparison.InvariantCultureIgnoreCase);
                                         }
                                     );
                foreach (var element in targetElements)
                {
                    Console.WriteLine(element);
                }
            }

            Console.ReadLine();
        }

        private static string[] GetMergeAttr(XElement element)
        {
            string mergefield = (string)element.Attribute("mergefield");
            return mergefield.Split(',');
        }
    }
}

---

根据评论进行更新

我想以下是你需要的

XElement target = XElement.Parse(txml);
XElement source = XElement.Parse(sxml);
var targetMergeAttrs = GetMergeAttr(target);
var sourceMergeAttrs = GetMergeAttr(source);

foreach (var sourceElement in source.Elements())
{
        foreach(var mergeField in sourceMergeAttrs)
        {

            if(sourceElement.Attributes().Any(x=>x.Name.LocalName.Equals(mergeField)) &&
            target.Elements()
                  .Any(x=>x.Attributes()
                                      .Where(c=>c.Name.LocalName == mergeField 
                                      && targetMergeAttrs.Contains(mergeField)
                                      && c.Value == (string)sourceElement.Attribute(mergeField)).Any()
                                      ))
            {
                XElement targetElement = target.Elements()
                  .FirstOrDefault(x=>x.Attributes()
                                      .Where(c=>c.Name.LocalName == mergeField 
                                      && targetMergeAttrs.Contains(mergeField)
                                      && c.Value == (string)sourceElement.Attribute(mergeField)).Any()
                                      );
                // Do work with targetElement 
                break;
            }

        }
}

---

合并字段是否总是用逗号分隔？如果是，您可以使用String.Split并返回这两个字段。@zanseb是的，它们被逗号分隔。我无法提出正确的LINQ查询，它不断抛出异常@đěxě，可能是我。我重新组织了一个问题，使其能够运行。您的困难是“提取要查找的值”还是“检查多个值”？这些是可分离的任务。不清楚你在问什么。请编辑有关

目标

、

源

和预期输出的问题、更多解释和示例。我上面的示例返回“序列包含多个匹配元素异常”请查看我在文章中的最后一个代码部分。如果我有两个合并字段，这就行了。我希望它能适用于任意数量的合并字段。秩序并不重要matter@EricKlaus看来还有一场比赛。在这种情况下应该怎么做？不应该有多个匹配项。它要么是blah，要么是blahblahThis几乎可以工作，但这里的目标元素也可能有空值。是否可以将targetElement XElement改为var？\这取决于具体情况。如果可以确保始终存在匹配项，则可以调用

Single

，而不是

SingleOrDefault

。否则，您可以将

IEnumerable

强制转换为列表。

using System;
using System.Linq;
using System.Xml.Linq;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            var path = (@"PATH");
            XElement target = XElement.Load(path);
            XElement source = XElement.Load(path);
            var mergefields = GetMergeAttr(target);

            foreach (var sourceElement in source.Elements())
            {
                var targetElements = from mergefield in mergefields
                                     select target.Elements().SingleOrDefault(t => 
                                         {
                                             if (t.Attribute(mergefield) == null || sourceElement.Attribute(mergefield) == null)
                                             {
                                                 return false;
                                             }

                                             return String.Equals(
                                             t.Attribute(mergefield).Value,
                                             sourceElement.Attribute(mergefield).Value,
                                             StringComparison.InvariantCultureIgnoreCase);
                                         }
                                     );
                foreach (var element in targetElements)
                {
                    Console.WriteLine(element);
                }
            }

            Console.ReadLine();
        }

        private static string[] GetMergeAttr(XElement element)
        {
            string mergefield = (string)element.Attribute("mergefield");
            return mergefield.Split(',');
        }
    }
}

XElement target = XElement.Parse(txml);
XElement source = XElement.Parse(sxml);
var targetMergeAttrs = GetMergeAttr(target);
var sourceMergeAttrs = GetMergeAttr(source);

foreach (var sourceElement in source.Elements())
{
        foreach(var mergeField in sourceMergeAttrs)
        {

            if(sourceElement.Attributes().Any(x=>x.Name.LocalName.Equals(mergeField)) &&
            target.Elements()
                  .Any(x=>x.Attributes()
                                      .Where(c=>c.Name.LocalName == mergeField 
                                      && targetMergeAttrs.Contains(mergeField)
                                      && c.Value == (string)sourceElement.Attribute(mergeField)).Any()
                                      ))
            {
                XElement targetElement = target.Elements()
                  .FirstOrDefault(x=>x.Attributes()
                                      .Where(c=>c.Name.LocalName == mergeField 
                                      && targetMergeAttrs.Contains(mergeField)
                                      && c.Value == (string)sourceElement.Attribute(mergeField)).Any()
                                      );
                // Do work with targetElement 
                break;
            }

        }
}