使用LINQ搜索XML文档

Question

I have an xml doc similar to this:

<Root>

    <MainItem ID="1">
        <SubItem></SubItem>
        <SubItem></SubItem>
        <SubItem></SubItem>
    </MainItem>
    <MainItem ID="2">
        <SubItem></SubItem>
        <SubItem></SubItem>
        <SubItem></SubItem>
    </MainItem>

    ...
</Root>

I want to return the whole of the MainItem element based on the value of attribute ID. So effectively if Attribute ID is equal to 2, then give me that MainItem element back.

I can't work out how to do this with LINQ. There seems to be a load of information on google, but I just can't quite seem to find what I'm looking for.

Little help ?

TIA

:-)

Answer 1

It could be something like this:

        XDocument doc = XDocument.Load("myxmlfile.xml");
        XElement mainElement = doc.Element("Root")
                                    .Elements("MainItem")
                                    .First(e => (int)e.Attribute("ID") == 2);
        // additional work

Answer 2

How about this:

// load your XML
XDocument doc = XDocument.Load(@"D:\linq.xml");

// find element which has a ID=2 value
XElement mainItem = doc.Descendants("MainItem")
                          .Where(mi => mi.Attribute("ID").Value == "2")
                          .FirstOrDefault();

if(mainItem != null)
{ 
  // do whatever you need to do
}

Marc

Answer 3

I changed your XML slightly to have values:

<?xml version="1.0"?>
<Root>
    <MainItem ID="1">
        <SubItem>value 1</SubItem>
        <SubItem>val 2</SubItem>
        <SubItem></SubItem>
    </MainItem>
    <MainItem ID="2">
        <SubItem></SubItem>
        <SubItem></SubItem>
        <SubItem></SubItem>
    </MainItem>
</Root>

And with this LINQ:

XDocument xmlDoc = XDocument.Load(@"C:\test.xml");
var result = from mainitem in xmlDoc.Descendants("MainItem")
             where mainitem.Attribute("ID").Value == "1"
             select mainitem;


foreach (var subitem in result.First().Descendants())
{
    Console.WriteLine(subitem.Value);
}

Console.Read();

Answer 4

From here: How to: Filter on an Attribute (XPath-LINQ to XML)

// LINQ to XML query
IEnumerable<XElement> list1 =
    from el in items.Descendants("MainItem")
    where (string)el.Attribute("ID") == "2"
    select el;

// XPath expression
IEnumerable<XElement> list2 = items.XPathSelectElements(".//MainItem[@ID='2']");