How to group XML data using LINQ in C#.net?

Question

I want to read an xml file using C#.net and with help of LINQ i want to group the nodes in xml based on INSTANCE and CINSTANCE values. How can i do that? This is my source schema:

<XYZ>
    <TYPE>A</TYPE>
    <INSTANCE>1357599</INSTANCE>
    <CHILD>DESCRIPTION</CHILD>
    <CINSTANCE>PQR</CINSTANCE>
    <CPOS>0000</CPOS>
    </XYZ>

    <XYZ>
    <TYPE>GP</TYPE>
    <INSTANCE>1472422</INSTANCE>
    <CHILD>A</CHILD>
    <CINSTANCE>1357599</CINSTANCE>
    <CPOS>0010</CPOS>
    </XYZ>

    <XYZ>
    <TYPE>GP</TYPE>
    <INSTANCE>1472427</INSTANCE>
    <CHILD>A</CHILD>
    <CINSTANCE>1357599</CINSTANCE>
    <CPOS>0010</CPOS>
    </XYZ>

    <XYZ>
    <TYPE>A</TYPE>
    <INSTANCE>1357600</INSTANCE>
    <CHILD>DESCRIPTION</CHILD>
    <CINSTANCE>PQR</CINSTANCE>
    <CPOS>0000</CPOS>
    </XYZ>

    <XYZ>
    <TYPE>GP</TYPE>
    <INSTANCE>1472425</INSTANCE>
    <CHILD>A</CHILD>
    <CINSTANCE>1357600</CINSTANCE>
    <CPOS>0010</CPOS>
    </XYZ>

    <XYZ>
    <TYPE>GP</TYPE>
    <INSTANCE>1472426</INSTANCE>
    <CHILD>A</CHILD>
    <CINSTANCE>1357600</CINSTANCE>
    <CPOS>0010</CPOS>
    </XYZ>

This should be my output:

<Group>
    <XYZ>
<TYPE>A</TYPE>
<INSTANCE>1357599</INSTANCE>
<CHILD>DESCRIPTION</CHILD>
<CINSTANCE>PQR</CINSTANCE>
<CPOS>0000</CPOS>
</XYZ>

    <XYZ>
<TYPE>GP</TYPE>
<INSTANCE>1472422</INSTANCE>
<CHILD>A</CHILD>
<CINSTANCE>1357599</CINSTANCE>
<CPOS>0010</CPOS>
</XYZ>

    <XYZ>
<TYPE>GP</TYPE>
<INSTANCE>1472427</INSTANCE>
<CHILD>A</CHILD>
<CINSTANCE>1357599</CINSTANCE>
<CPOS>0010</CPOS>
</XYZ>
    </Group>    

    <Group>
    <XYZ>
<TYPE>A</TYPE>
<INSTANCE>1357600</INSTANCE>
<CHILD>DESCRIPTION</CHILD>
<CINSTANCE>PQR</CINSTANCE>
<CPOS>0000</CPOS>
</XYZ>

    <XYZ>
<TYPE>GP</TYPE>
<INSTANCE>1472425</INSTANCE>
<CHILD>A</CHILD>
<CINSTANCE>1357600</CINSTANCE>
<CPOS>0010</CPOS>
</XYZ>

    <XYZ>
<TYPE>GP</TYPE>
<INSTANCE>1472426</INSTANCE>
<CHILD>A</CHILD>
<CINSTANCE>1357600</CINSTANCE>
<CPOS>0010</CPOS>
</XYZ>
    </Group>

I need to group XYZ nodes based on INSTANCE==CINSTANCE ..Is there anyway to write a logic for this?

Answer 1

You're probably looking for something like the code below, but a minor change is required to your format, it needs a valid parent element in the Xml.

    static void Main(string[] args)
    {
        string xml = @"<ELEMENTS><XYZ>     <TYPE>A</TYPE>     <INSTANCE>1357599</INSTANCE>     <CHILD>DESCRIPTION</CHILD>     <CINSTANCE>PQR</CINSTANCE>     <CPOS>0000</CPOS>     </XYZ>      <XYZ>     <TYPE>GP</TYPE>     <INSTANCE>1472422</INSTANCE>     <CHILD>A</CHILD>     <CINSTANCE>1357599</CINSTANCE>     <CPOS>0010</CPOS>     </XYZ>      <XYZ>     <TYPE>GP</TYPE>     <INSTANCE>1472427</INSTANCE>     <CHILD>A</CHILD>     <CINSTANCE>1357599</CINSTANCE>     <CPOS>0010</CPOS>     </XYZ>      <XYZ>     <TYPE>A</TYPE>     <INSTANCE>1357600</INSTANCE>     <CHILD>DESCRIPTION</CHILD>     <CINSTANCE>PQR</CINSTANCE>     <CPOS>0000</CPOS>     </XYZ>      <XYZ>     <TYPE>GP</TYPE>     <INSTANCE>1472425</INSTANCE>     <CHILD>A</CHILD>     <CINSTANCE>1357600</CINSTANCE>     <CPOS>0010</CPOS>     </XYZ>      <XYZ>     <TYPE>GP</TYPE>     <INSTANCE>1472426</INSTANCE>     <CHILD>A</CHILD>     <CINSTANCE>1357600</CINSTANCE>     <CPOS>0010</CPOS>     </XYZ></ELEMENTS>";
        Console.WriteLine(GetGroups(xml).ToString());
    }

    private static XDocument GetGroups(string xml)
    {
        XDocument xyzElementsDocument = XDocument.Parse(xml);

        var results = from xyzElement1 in xyzElementsDocument.Descendants("XYZ")
                      join xyzElement2 in xyzElementsDocument.Descendants("XYZ")
                      on (string)xyzElement1.Element("INSTANCE") equals (string)xyzElement2.Element("CINSTANCE") into joinedElements
                      from joinedElement in joinedElements.DefaultIfEmpty()
                      group xyzElement1 by joinedElement != null into groupedElements
                      select new { HasCInstance = groupedElements.Key, Elements = groupedElements.Distinct() };

        XDocument groupDocument = new XDocument();
        groupDocument.Add(new XElement("GROUPS"));
        foreach (var result in results)
        {
            XElement groupElement = new XElement("GROUP");
            groupElement.Add(result.Elements);
            groupDocument.Root.Add(groupElement);
        }

        return groupDocument;
    }