如何使用 LINQ 读取指定的 xml 节点值？

Question

当我指定 VM 名称值时，我想从附加的 xml 文件中读取浏览器和语言值。我尝试多次运行以下方法，但我不断收到错误。任何人都可以建议我的代码修复或更好的方法来获得我想要的东西吗？ 非常感谢。 J.

<?xml version='1.0' encoding='utf-8'?>
<automationSettings>

<!--VM settings on ESX Server-->
<VM name="DE-2K8" language="de" powerOn="true">
    <vmClients>
        <vmClient name="ITXP" language="it"/>
    </vmClients>
    <guest>
        <browser value = "firefox"/>
        <language value = "de"/>
    </guest>
</VM>

<VM name="EN2008" language="en" powerOn="true">
    <vmClients>
        <vmClient name="IT-2K8R2ENT64X" language="it"/>
    </vmClients>
    <guest>
        <browser value = "chrome"/>
        <language value = "en"/>
    </guest>
</VM>

</automationSettings>

这是我用来尝试获取浏览器或语言值的代码：

public static string ReadVMSettings(string systemName, string section, string name)
{
    try
    {
        systemsFilePath = @"C:\Text.xml";
        Console.WriteLine("Systems.xml path is: " + systemsFilePath);
        XDocument systemXML = XDocument.Load(systemsFilePath);

        var result = from vm in systemXML.Descendants("automationSettings")
                     .Descendants("VM")
                     .Descendants(section)
                     where vm.Attribute("name").Value == systemName
                     select vm.Element(name).Attribute("value").Value;
        return result.First();
    }

    catch (Exception ex)
    {
        Console.WriteLine("ReadVMSettings exception: " + ex.ToString());
        return string.Empty;
    }
}

这样称呼它： ReadVMSettings("EN2008", "guest", "language");

感谢。

Answer 1

您的 xml 模式中缺少根元素

你的Xml应该是这样的

<?xml version="1.0" encoding="utf-8" ?>
<automationSettings> //missing root element
<VM name="DE-2K8" language="de" powerOn="true">
  <vmClients>
    <vmClient name="ITXP" language="it"/>
  </vmClients>
  <guest>
    <browser value = "firefox"/>
    <language value = "de"/>
  </guest>
</VM>

<VM name="EN2008" language="en" powerOn="true">
  <vmClients>
    <vmClient name="IT-2K8R2ENT64X" language="it"/>
  </vmClients>
  <guest>
    <browser value = "chrome"/>
    <language value = "en"/>
  </guest>
</VM>
</automationSettings> 

给你...

    static void Main(string[] args)
    {
        string value = ReadVMSettings("EN2008", "guest", "browser");
    }

    public static string ReadVMSettings(string systemName, string section, string name)
    {
        string systemsFilePath = @"C:\Text.xml";
        Console.WriteLine("Systems.xml path is: " + systemsFilePath);
        XDocument systemXML = XDocument.Load(systemsFilePath);
        var result = from vm in systemXML.Root.Descendants("VM")
                     where vm.Attribute("name").Value == systemName
                     select vm.Element(section).Element(name).Attribute("value").ToString();
        return result.FirstOrDefault().ToString();

    }

Answer 2

这应该返回您在示例中寻找的语言值。

string val = SettingFromXML(
    @"<!--VM settings on ESX Server-->                
    <VM name=""DE-2K8"" language=""de"" powerOn=""true"">
        <vmClients>
            <vmClient name=""ITXP"" language=""it""/>
        </vmClients>
        <guest>
            <browser value = ""firefox""/>
            <language value = ""de""/>
        </guest>
    </VM>
    <VM name=""EN2008"" language=""en"" powerOn=""true"">
        <vmClients>
            <vmClient name=""IT-2K8R2ENT64X"" language=""it""/>
        </vmClients>
        <guest>
            <browser value = ""chrome""/>
            <language value = ""en""/>
        </guest>
    </VM>", "EN2008", "guest", "language"
);
MessageBox.Show(val);

public static string SettingFromXML(string xml, string systemName, string section, string name) {
    xml = "<VMSettings>" + xml + "</VMSettings>"; // wrap XML in root node to deal with multiple root node exception
    using (MemoryStream ms = new MemoryStream(Encoding.Default.GetBytes(xml))) {
        XDocument xDoc = XDocument.Load(ms);
        return xDoc.Descendants("VMSettings")
                   .Descendants("VM").First(el1 => el1.Attribute("name").Value == systemName)
                   .Descendants().First(el2 => el2.Name == section)
                   .Descendants().First(el3 => el3.Name == name).Attribute("value").Value;                
    }                
}