How to: Create Hierarchy Using Grouping

This example shows how to group data, and then generate XML based on the grouping.

Example

This example first groups data by a category, then generates a new XML file in which the XML hierarchy reflects the grouping.

This example uses the following XML document: Sample XML File: Numerical Data (LINQ to XML).

XElement doc = XElement.Load("Data.xml");
var newData =
    new XElement("Root",
        from data in doc.Elements("Data")
        group data by (string)data.Element("Category") into groupedData
        select new XElement("Group",
            new XAttribute("ID", groupedData.Key),
            from g in groupedData
            select new XElement("Data",
                g.Element("Quantity"),
                g.Element("Price")
            )
        )
    );
Console.WriteLine(newData);

Dim doc As XElement = XElement.Load("Data.xml")
Dim newData As XElement = _
    <Root>
        <%= _
            From data In doc.<Data> _
            Group By category = data.<Category>(0).Value _
            Into groupedData = Group _
            Select <Group ID=<%= category %>>
                       <%= _
                           From g In groupedData _
                           Select _
                           <Data>
                               <%= g.<Quantity>(0) %>
                               <%= g.<Price>(0) %>
                           </Data> _
                       %>
                   </Group> _
        %>
    </Root>
Console.WriteLine(newData)

This example produces the following output:

<Root>
  <Group ID="A">
    <Data>
      <Quantity>3</Quantity>
      <Price>24.50</Price>
    </Data>
    <Data>
      <Quantity>5</Quantity>
      <Price>4.95</Price>
    </Data>
    <Data>
      <Quantity>3</Quantity>
      <Price>66.00</Price>
    </Data>
    <Data>
      <Quantity>15</Quantity>
      <Price>29.00</Price>
    </Data>
  </Group>
  <Group ID="B">
    <Data>
      <Quantity>1</Quantity>
      <Price>89.99</Price>
    </Data>
    <Data>
      <Quantity>10</Quantity>
      <Price>.99</Price>
    </Data>
    <Data>
      <Quantity>8</Quantity>
      <Price>6.99</Price>
    </Data>
  </Group>
</Root>

See Also

Concepts

Advanced Query Techniques (LINQ to XML)