C＃Linq XML Query存在多个同名元素

Question

Linq newbie here. Did the searching, and couldn't find an exact question; tried to work from other answers that were similar , but still couldn't get it.

Having trouble returning all instances of a particular element name. I can get one item returned, just not them all.

Here is the XML:

<?xml version="1.0"?>
<printerlist>
  <list type="aff">
    <printserver>print-server1</printserver>
    <printserver>print-server2</printserver>
    <printserver>print-server3</printserver>
  </list>
  <list type="lff">
    <printserver>print-sever4</printserver>
    <additionalprinters>
      <printer>
        <fullname>\\serverb\bbb</fullname>
      </printer>
      <printer>
        <fullname>\\serverc\aaa</fullname>
      </printer>
    </additionalprinters>
  </list>
</printerlist>

And here is the code to try and get the list:

var query = from c in xml.Root.Descendants("list")
    where (string)c.Attribute("type") == "aff"
    select c.Element("printserver");

foreach (string name in query)
{
    Console.WriteLine("Server Name: {0}", name);
}

This only produces the first element of printserver: print-server1 How can I get the foreach to list all 3 servers that are in the aff list?

Thanks

Answer 1

You need to use Elements("printserver") instead of Element("printserver") like so :

var query = (from c in doc.Root.Descendants("list").Elements("printserver")
             where (string)c.Parent.Attribute("type") == "aff"
             select c);

or using SelectMany() like this :

var query = (from c in doc.Root.Descendants("list")
             where (string)c.Attribute("type") == "aff"
             select c).SelectMany(c => c.Elements("printserver"));

or if you are sure only one element match the where clause, you can use First() like this :

var query = (from c in doc.Root.Descendants("list")
             where (string)c.Attribute("type") == "aff"
             select c).First().Elements("printserver"));

Answer 2

How about something like this:

List<XElement> elements = doc.Root.Descendants("printserver")
                                 .Where(e => e.Parent.Name == "list" && e.Parent.Attribute("type").Value == "aff")
                                 .ToList();

Then, if you want to loop through the elements:

foreach (XElement e in elements)
{
    Console.WriteLine("Server Name : {0}", e.Value);
}

If you just want the string-values of each printserver, use a .Select at the end:

List<string> elements = doc.Root.Descendants("printserver")
                                .Where(e => e.Parent.Name == "list" && e.Parent.Attribute("type").Value == "aff")
                                .Select(p => p.Value)
                                .ToList();

Above solution allows the use of your current foreach-loop.