Question

Here is my XML sample. I want to select SystemSetting’s value if ID = 123. But I can’t figure out how. How can I select SystemSetting value if id’s value equal to 123 ?

<?xml version="1.0" encoding="utf-8" ?>
<Private>
  <System>
    <ID>123</ID>
    <NAME>Test</NAME>
    <SystemSetting>128</SystemSetting>
    <SystemSettingCS>127</SystemSettingCS>
  </System> 
  <System>
    <ID>124</ID>
    <NAME>Test2</NAME>
    <SystemSetting>128</SystemSetting>
    <SystemSettingCS>127</SystemSettingCS>
  </System>
  <System>
    <ID>0</ID>
    <NAME>Test</NAME>   
    <SystemSetting>5</SystemSetting>
    <SystemSettingCS>250</SystemSettingCS>
  </System>
</Private>

Here’s what I tried:

    var doc = XDocument.Load(Application.StartupPath+  @"\Settings.xml");
    var q = from Ana in doc.Descendants("Private")                   
            from sistem in Ana.Elements("System")                   
            where (int)sistem.Element("ID") == 123
            from assetText in Sistem.Elements("System")
            select assetText.Element("SystemSetting");

    MessageBox.Show(q.ToString());

thnx for help.

Answer 1

I think you’re making this more complicated than you need to. I think you just need:

var query = doc.Descendants("Private") // Or just doc.Root
               .Elements("System")
               .Where(x => (int) x.Element("ID") == 123)
               .Select(x => x.Element("SystemSetting"))
               .FirstOrDefault();

That will select the first matching element, admittedly. The type of query is then XElement; if you take off the FirstOrDefault() part, it will return an IEnumerable<XElement>, for all matching elements.

If you want just the value instead of the element, you can change the Select to:

.Select(x => (string) x.Element("SystemSetting"))

or

.Select(x => x.Element("SystemSetting").Value)

(The first will return null if there’s no SystemSetting element; the second will throw an exception.)