的LINQ to XML查询的同级元素 [英] LINQ to XML querying for sibling elements

问题描述

很抱歉，如果这个问题是非常基本的，但我还没有与XML非常多，这是我第一次使用LINQ合作，XML ...

Sorry if this question is very basic, but I haven't worked with XML very much, and this is my first time working with LINQ to XML...

我有一个结构类似于一个目录树一个XML站点地图：

I have an XML sitemap that is structured like a directory tree:

<Site>
    <File GUID="xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx">FileName</file>
    <Folder name="FolderName">
        <Security>
            <Role>Admin</role>
        </Security>
        <File GUID="xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx">FileName</file>
        <Folder name="subFoler">
            <File GUID="xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx">FileName</file>
            <File GUID="xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx">FileName</file>
            <Folder>
                <File GUID="xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx">FileName</file>
            </Folder>
        </Folder>
    </Folder>
</Site>

在这种方式，每个文件将继承的安全性，从它的父文件夹（或祖父母文件夹，等等，这取决于有多少了树＆LT;安全＆GT;＆LT; /安全＆GT; 的位置。

In this way, every file will inherit security from its parent folder (or grandparent folder, etc, depending upon how far up the tree the <security></security> is located.

我希望能给出一个文件的GUID，选择使用LINQ该文件，并收集所有与该文件继承了安全相关的职务。

I want to be able to, given a file's GUID, select that file with LINQ, and gather all of the roles associated with the security that file has inherited.

这是我迄今为止，但它是一个非常粗略的尝试，是不完整的：

This is what I have so far, but it is a very rough attempt, and is not complete:

XDocument sitemap = XDocument.Load(@"\sitemap.xml");
XElement currentFile = new XElement("File", 
        from file in sitemap.Elements("File")
        where file.Element("GUID").Equals(guid)
        select file.Parent.Element("security").Elements("role"));

PS。站点地图文件位于同一目录中，该code被写入在类中

ps. The sitemap file is located within the same directory as the class in which this code is written

推荐答案

看起来要走上文件夹祖先链和积累的角色找到前进的道路上。你可以做到这一点与贴切的名字祖先（）和<一HREF =htt​​p://msdn.microsoft.com/en-us/library/bb534336.aspx相对=nofollow>的SelectMany（）方法：

It looks like you want to walk up the folder ancestor chain and accumulate the roles you find along the way. You can do that with the aptly-named Ancestors() and SelectMany() methods:

XElement fileFromMap = sitemap.Descendants("File").Where(
    file => file.Attribute("GUID").Value == guid.ToString("D")).Single();

XElement currentFile = new XElement("File",
    fileFromMap.Value,
    fileFromMap.Ancestors("Folder").SelectMany(
        folder => {
            XElement security = folder.Element("Security");
            return (security != null
                ? security.Elements("Role") : new XElement[0]);
        }));

编辑：更改元素资本，以配合更新的问题

Changed element capitalization to match the updated question.

编辑2：的code以上被误喂空项目的SelectMany（）（比 XElement.Add（）在这方面），而这个的导致 NullPointerException异常 。它已被更新，以返回一个空的XElement 阵列代替。

EDIT 2: The code above was mistakenly feeding a null item to SelectMany() (which is far less indulgent than XElement.Add() in this regard), and this resulted in a NullPointerException. It has been updated to return an empty XElement array instead.

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