Question

I have the following XML structure:

<Capabilities>
    <Capability ID="1" Name="Capability # 1">
        <Relations>
            <Relation RelatedTo="2" RelationType="Child"/>
            <Relation RelatedTo="3" RelationType="Child"/>
            <Relation RelatedTo="4" RelationType="Child"/>
            <Relation RelatedTo="5" RelationType="Child"/>
        </Relations>
    </Capability>
    <Capability ID="3" Name="Capability # 3">
        <Relations>
            <Relation RelatedTo="1" RelationType="Dependant" />
        </Relations>
    </Capability>
    <Capability ID="2" Name="Capability # 2">
        <Relations>
            <Relation RelatedTo="6" RelationType="Child" />
            <Relation RelatedTo="5" RelationType="Child" />
        </Relations>
    </Capability>
</Capabilities>

And I need to query the for all Capabilities with a Child relation with RelatedTo attribute of value 5.
So far I’ve tried with the following query but I get a collection of ‘null reference exceptions’ and I can’t figure out how to do it.

   var result = root.Elements("Capability")
                 .Where(c => c.Elements("Relations")
                            .Where(r => r.Attribute("RelatedTo").Value == "5"
                                && r.Attribute("").Value == Enum.GetName(typeof(RelationTypes), RelationTypes.Children)).Any());

Any clues on what I’m doing wrong or what’s the correct way to query it?

Answer 1

var capabilites = root.Descendants("Capability")
            .Where(c => c.Descendants("Relation")
                         .Any(r => (string)r.Attribute("RelatedTo") == "5"))
            .ToList();