代码之家 › 专栏 › 技术社区 › Rico Strydom

Linq to XML:如何基于文件中的其他元素获取元素

linq-to-xml lambda xml c#

Rico Strydom · 技术社区 · 1 年前

考虑以下xml文件。我想得到 ConnectionString 如果我已经有了元素 Environment/Name 价值和 Application/Name 从不同的 ComboBoxes .

<?xml version="1.0" encoding="utf-8" ?>
<Environments>
    <Environment>
        <Name>DEV</Name>
        <Applications>
            <Application>
                <Name>App1</Name>
                <DBType>Oracle</DBType>
                <ConnectionString>CS1</ConnectionString>
                <Username>user_1</Username>
                <Password>pw_1</Password>               
            </Application>
            <Application>
                <Name>App2</Name>
                <DBType>Oracle</DBType>                     
                <ConnectionString>CS2</ConnectionString>
                <Username>user_2</Username>
                <Password>pw_2</Password>
            </Application>          
        </Applications>
    </Environment>
    <Environment>
        <Name>TEST 1</Name>
        <Applications>
            <Application>
                <Name>App1</Name>
                <DBType>Oracle</DBType> 
                <ConnectionString>CS3sername>
                <Password>pw_3</Password>               
            </Application>
            <Application>
                <Name>App2</Name>
                <DBType>Oracle</DBType>             
                <ConnectionString>CS4</ConnectionString>
                <Username>user_4</Username>
                <Password>pw_4</Password>
            </Application>  
        </Applications>
    </Environment>
</Environments>

这就是我现在所拥有的,但我没有得到任何结果。

XDocument xDocument = XDocument.Load("Environments.xml");
        IEnumerable<XElement> ConnectionString = xDocument
        .XPathSelectElements("/Environments/Environment/Applications/Application/ConnectionString")
        .Where(x => x.XPathSelectElements("/Environments/Environment/Name").All(x => x.Value.Equals(Environment1ComboBox.SelectedItem))
                && x.XPathSelectElements("/Environments/Environment/Applications/Application/Name").All(x => x.Value.Equals(Application1ComboBox.SelectedItem)))
        .ToList();

2 回复 | 直到 1 年前

Yitzhak Khabinsky 1 年前

这是通过LINQ to XML的另一种方法,使用 Ancestors() 方法。

它允许直接进入 连接串 在检查其祖先值的同时,在一个语句中检查元素。

void Main()
{
     const string FILENAME = @"e:\Temp\Environments.xml";

    string environmentName = "DEV"; //Environment1ComboBox.SelectedItem;
    string applicationName = "App2"; //Application1ComboBox.SelectedItem;
    
    XDocument xdoc = XDocument.Load(FILENAME);

    string connectionString = xdoc.Descendants("ConnectionString")?
        .Where(x => x.Ancestors("Environment").Elements("Name")
            .FirstOrDefault().Value == environmentName 
            &&
            x.Ancestors("Application").Elements("Name")
            .FirstOrDefault().Value == applicationName)
            .FirstOrDefault().Value;
    Console.WriteLine(connectionString);
}

输出

CS2

Jon Skeet 1 年前

说实话,我不会使用XPath来实现这一点。为了简单起见,我将分两步完成,一步是获取环境,另一步是其中的应用程序:

// Cast if you need to...
string environmentName = Environment1ComboBox.SelectedItem;
string applicationName = Application1ComboBox.SelectedItem;

// First get the matching environment.
var document = XDocument.Load("Environments.xml");
var environment = document.Root?
    .Elements("Environment")
    .FirstOrDefault(env => (string) env.Element("Name") == environmentName);
if (environment is null)
{
    // Report that the environment isn't found, and exit this code
}

// Now get the matching application within the environment.
var application = environment
    .Element("Applications")
    .Elements("Application")
    .FirstOrDefault(app => (string) app.Element("Name") == applicatoinName);
if (application is null)
{
    // Report that the application isn't found, and exit this code
}

// Now we can get the connection string.
string connectionString = (string) app.Element("ConnectionString");