Linq to XML, select all attributes and their values for a given node

linq linq-to-xml

12,098

Solution 1

Update

Summarized in a method:

public IEnumerable<XAttribute> GetAttributes(string modelName, string colour)
{
    XDocument mappings = XDocument.Load(@"D:\colour_mappings.xml");

    var q1 =
        from elm in mappings.Descendants("model")
        where (string)elm.Attribute("name") == "modelY"
        select elm;

    var q2 =
        from elm in q1.Descendants("mapping")
        where (string)elm.Attribute("colour") == "White"
        select elm.Attributes().Where(a => a.Name != "colour");


    foreach (IEnumerable<XAttribute> attributeList in q2)
    {
        foreach (XAttribute attribute in attributeList)
        {
            yield return attribute;
        }
    }
}

Solution 2

as I am pushed for time I will use a 2 stage process

But would be interested to hear if this is possible in one query

var matchingModelXml = from c in mappings.Descendants("model")
                               where (string)c.Attribute("name") == "modelY"
                               select c;

var mappingAttributes = from b in matchingModelXml.Descendants("mapping")
                        where (string)b.Attribute("colour") == "White"
                        select b.Attributes();

Solution 3

Just because I like a challenge, here it is in one query:

XDocument test = XDocument.Parse("<colourMappings>    <model name=\"modelX\">        <mapping colour=\"White\" configCode=\"1\"></mapping>        <mapping colour=\"Aluminium\" configCode=\"2\"></mapping>        <mapping colour=\"Black\" configCode=\"3\"></mapping>        <mapping colour=\"Blue\" configCode=\"4\"></mapping>        <mapping colour=\"White Pearl\" configCode=\"5\"></mapping>        <mapping colour=\"Graphite\" configCode=\"6\"></mapping>        <mapping colour=\"Gunmetal\" configCode=\"7\"></mapping>        <mapping colour=\"Indigo\" configCode=\"8\"></mapping>        <mapping colour=\"Red\" configCode=\"9\"></mapping>    </model>    <model name=\"modelY\">        <mapping colour=\"White\" configCode=\"1\" stConfigCode= \"xx\" dgConfigCode=\"hj\"></mapping>        <mapping colour=\"Aluminium\" configCode=\"2\" stConfigCode= \"xy\" dgConfigCode=\"gh\"></mapping>        <mapping colour=\"Black\" configCode=\"3\" stConfigCode= \"xt\" dgConfigCode=\"fg\"></mapping>        <mapping colour=\"Blue\" configCode=\"4\" stConfigCode= \"sd\" dgConfigCode=\"fg\"></mapping>        <mapping colour=\"White Pearl\" configCode=\"5\" stConfigCode= \"df\" dgConfigCode=\"df\"></mapping>        <mapping colour=\"Graphite\" configCode=\"6\" stConfigCode= \"xc\" dgConfigCode=\"df\"></mapping>        <mapping colour=\"Gunmetal\" configCode=\"7\"  stConfigCode= \"cv\" dgConfigCode=\"cv\"></mapping>        <mapping colour=\"Indigo\" configCode=\"8\"  stConfigCode= \"zx\" dgConfigCode=\"vb\"></mapping>        <mapping colour=\"Red\" configCode=\"9\"  stConfigCode= \"fg\" dgConfigCode=\"cv\"></mapping>    </model></colourMappings>");

var maps = from model in test.Root.Elements("model")
           from attr in model.Attributes("name")
           from mapping in model.Elements("mapping")
           where attr.Value == "modelY" && mapping.Attribute("colour").Value == "White"
           select new
           {
                 configCode = mapping.Attribute("configCode").Value
               , stConfigCode = mapping.Attribute("stConfigCode").Value
               , dgConfigCode = mapping.Attribute("dgConfigCode").Value
           };

foreach (var map in maps)
{
    Console.Write("configCode: ");
    Console.WriteLine(map.configCode);
    Console.Write("stConfigCode: ");
    Console.WriteLine(map.stConfigCode);
    Console.Write("dgConfigCode: ");
    Console.WriteLine(map.dgConfigCode);
}

12,098

Author by

ChrisCa

Updated on June 05, 2022

Comments

ChrisCa almost 2 years

I have an xml mapping file that looks something like this

<colourMappings>
    <model name="modelX">
        <mapping colour="White" configCode="1"></mapping>
        <mapping colour="Aluminium" configCode="2"></mapping>
        <mapping colour="Black" configCode="3"></mapping>
        <mapping colour="Blue" configCode="4"></mapping>
        <mapping colour="White Pearl" configCode="5"></mapping>
        <mapping colour="Graphite" configCode="6"></mapping>
        <mapping colour="Gunmetal" configCode="7"></mapping>
        <mapping colour="Indigo" configCode="8"></mapping>
        <mapping colour="Red" configCode="9"></mapping>
    </model>
    <model name="modelY">
        <mapping colour="White" configCode="1" stConfigCode= "xx" dgConfigCode="hj"></mapping>
        <mapping colour="Aluminium" configCode="2" stConfigCode= "xy" dgConfigCode="gh"></mapping>
        <mapping colour="Black" configCode="3" stConfigCode= "xt" dgConfigCode="fg"></mapping>
        <mapping colour="Blue" configCode="4" stConfigCode= "sd" dgConfigCode="fg"></mapping>
        <mapping colour="White Pearl" configCode="5" stConfigCode= "df" dgConfigCode="df"></mapping>
        <mapping colour="Graphite" configCode="6" stConfigCode= "xc" dgConfigCode="df"></mapping>
        <mapping colour="Gunmetal" configCode="7"  stConfigCode= "cv" dgConfigCode="cv"></mapping>
        <mapping colour="Indigo" configCode="8"  stConfigCode= "zx" dgConfigCode="vb"></mapping>
        <mapping colour="Red" configCode="9"  stConfigCode= "fg" dgConfigCode="cv"></mapping>
    </model>
</colourMappings>

I want to be able to pull out all the attributes and their values given a model name and colour

e.g.

given ModelY and White, I'd like to get configCode="1" stConfigCode= "xx" dgConfigCode="hj" This could be in any structure - array, list, whatever

I have been using Linq to XML but can't get the correct syntax

XDocument mappings = XDocument.Load(@"D:\colour_mappings.xml");
var q = from c in mappings.Descendants("model")
                    where (string)c.Attribute("name") == "modelY" && (string)c.Descendants("mapping").Attributes("colour").FirstOrDefault() == "White"
                    select c.Attributes();

anyone know how to do this?

Happy to use any method, doesn't necessarily need to be Linq

ChrisCa almost 14 years

thanks - that's not exactly what I need though. Your one returns all the attributes of every mapping I just want the attributes for the single mapping in ModelY that has a colour of white Decieded to do it as a 2 stage query - see below
Martin Ingvar Kofoed Jensen almost 14 years

@Christo Fur: Sorry, my mistake, just updated the code so it should work now :)
ChrisCa almost 14 years

thanks - I came to the same conclusion as you and did it in 2 steps
Martin Ingvar Kofoed Jensen almost 14 years

There is a way to do nested queries, but the code gets more complex, so I think this is the better solution
Martin Ingvar Kofoed Jensen almost 14 years

Nice :) Only need to remove the attribute 'colour', but thats easy :)
Martin Ingvar Kofoed Jensen almost 14 years

Just did some timings and it seems that your single query is 50-60% slower on this small sample set. I think the reason is that those 4 "from's" results in a lot of enumerating. But still a nice query :)
Matt Ellen almost 14 years

Thanks. I probably should have mentioned that I only wrote this for fun. I'd go the two query route too. It's easier to read as well as being faster :)
Matt Ellen almost 14 years

I've fiddled with the linq, so it should be a bit quicker, but still not as fast as 2 queries.