Question

I don’t often use Linq to query XML, and I don’t have a great deal of experience with XML. What I would like to do is to query this simple XML document…

<AlarmParameters>
    <Parameter>
        <ParameterName>ConsecutivePoints</ParameterName>
        <Points>30</Points>
        <AllowEdit>true</AllowEdit>
        <Caption>Consecutive Points</Caption>
    </Parameter>

    <Parameter>
        <ParameterName>SigmaCount</ParameterName>
        <Count>1</Count>
        <AllowEdit>true</AllowEdit>
        <Caption>Number of Sigmas</Caption>
    </Parameter>
</AlarmParameters>

… And produce a list of ‘Parameter’ classes, each containing the properties shown in the XML sample. Using LinqPad, I’ve managed to get this far, but don’t really know how to complete this.

string xmlFragment = "<AlarmParameters><Parameter><ParameterName>ConsecutivePoints</ParameterName><Points>30</Points><AllowEdit>true</AllowEdit><Caption>Consecutive Points</Caption></Parameter><Parameter><ParameterName>SigmaCount</ParameterName><Count>1</Count><AllowEdit>true</AllowEdit><Caption>Number of Sigmas</Caption></Parameter></AlarmParameters>";

StringReader strReader = new StringReader(xmlFragment);

XDocument xmlDoc = XDocument.Load(strReader);

var result = from parameter in xmlDoc (not sure what Linq to put here next)

Answer 1

You can find some good information looking at the LINQ to XML overview on MSDN. Here’s one way it could be done using the Descendants operator to pull out a collection of elements, and the Element operator to pull out the subproperties of each item in the collection:

var result =
    from parameter in xmlDoc.Descendants("Parameter")
    select new {
        ParameterName = (string) parameter.Element("ParameterName"),
        Points = (int?) parameter.Element("Points") ?? 0,
        Count = (int?) parameter.Element("Count") ?? 0,
        AllowEdit = (bool) parameter.Element("AllowEdit"),
        Caption = (string) parameter.Element("Caption")
    };

This just creates anonymous class instances, but you could replace with select new MyParameterClassName for your parameter class.