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How to transform the shape of an XML tree (LINQ to XML)

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The shape of an XML document refers to its element names, attribute names, and the characteristics of its hierarchy.

Sometimes you will have to change the shape of an XML document. For example, you might have to send an existing XML document to another system that requires different element and attribute names. You could go through the document, deleting and renaming elements as required, but using functional construction results in more readable and maintainable code. For more information about functional construction, see Functional construction.

The first example in this article changes the organization of an XML document. It moves complex elements from one location in the tree to another.

The second example creates an XML document whose shape differs from that of the source document. It omits some elements, renames others, and changes the casing of the element names.

Example: Use embedded query expressions to change the shape of an XML tree

The following example changes the shape of an XML file using embedded query expressions.

The source XML document for this example, Sample XML file: Customers and orders, contains a Customers element under the Root element that contains all customers. It also contains an Orders element under the Root element that contains all orders. The example creates a new XML tree in which the orders for each customer are contained in an Orders element within the Customer element. The original document also contains a CustomerID element in the Order element; this element is omitted from the new tree.

XElement co = XElement.Load("CustomersOrders.xml");
XElement newCustOrd =
    new XElement("Root",
        from cust in co.Element("Customers").Elements("Customer")
        select new XElement("Customer",
            cust.Attributes(),
            cust.Elements(),
            new XElement("Orders",
                from ord in co.Element("Orders").Elements("Order")
                where (string)ord.Element("CustomerID") == (string)cust.Attribute("CustomerID")
                select new XElement("Order",
                    ord.Attributes(),
                    ord.Element("EmployeeID"),
                    ord.Element("OrderDate"),
                    ord.Element("RequiredDate"),
                    ord.Element("ShipInfo")
                )
            )
        )
    );
Console.WriteLine(newCustOrd);

Dim co As XElement = XElement.Load("CustomersOrders.xml")
Dim newCustOrd = _
   <Root>
       <%= From cust In co.<Customers>.<Customer> _
           Select _
           <Customer>
               <%= cust.Attributes() %>
               <%= cust.Elements() %>
               <Orders>
                   <%= From ord In co.<Orders>.<Order> _
                       Where ord.<CustomerID>.Value = cust.@CustomerID _
                       Select _
                       <Order>
                           <%= ord.Attributes() %>
                           <%= ord.<EmployeeID> %>
                           <%= ord.<OrderDate> %>
                           <%= ord.<RequiredDate> %>
                           <%= ord.<ShipInfo> %>
                       </Order> _
                   %>
               </Orders>
           </Customer> _
       %>
   </Root>
Console.WriteLine(newCustOrd)

This example produces the following output:

<Root>
  <Customer CustomerID="GREAL">
    <CompanyName>Great Lakes Food Market</CompanyName>
    <ContactName>Howard Snyder</ContactName>
    <ContactTitle>Marketing Manager</ContactTitle>
    <Phone>(503) 555-7555</Phone>
    <FullAddress>
      <Address>2732 Baker Blvd.</Address>
      <City>Eugene</City>
      <Region>OR</Region>
      <PostalCode>97403</PostalCode>
      <Country>USA</Country>
    </FullAddress>
    <Orders />
  </Customer>
  <Customer CustomerID="HUNGC">
    <CompanyName>Hungry Coyote Import Store</CompanyName>
    <ContactName>Yoshi Latimer</ContactName>
    <ContactTitle>Sales Representative</ContactTitle>
    <Phone>(503) 555-6874</Phone>
    <Fax>(503) 555-2376</Fax>
    <FullAddress>
      <Address>City Center Plaza 516 Main St.</Address>
      <City>Elgin</City>
      <Region>OR</Region>
      <PostalCode>97827</PostalCode>
      <Country>USA</Country>
    </FullAddress>
    <Orders />
  </Customer>
  ...
</Root>

Example: Create a document whose shape differs from that of the source document

This example renames some elements and converts some attributes to elements. It calls ConvertAddress, which returns a list of XElement objects. The argument to the method is a query that determines the Address complex element where the Type attribute has a value of "Shipping". The example uses XML document Sample XML file: Typical purchase order.

static IEnumerable<XElement> ConvertAddress(XElement add)
{
    List<XElement> fragment = new List<XElement>() {
        new XElement("NAME", (string)add.Element("Name")),
        new XElement("STREET", (string)add.Element("Street")),
        new XElement("CITY", (string)add.Element("City")),
        new XElement("ST", (string)add.Element("State")),
        new XElement("POSTALCODE", (string)add.Element("Zip")),
        new XElement("COUNTRY", (string)add.Element("Country"))
    };
    return fragment;
}

static void Main(string[] args)
{
    XElement po = XElement.Load("PurchaseOrder.xml");
    XElement newPo = new XElement("PO",
        new XElement("ID", (string)po.Attribute("PurchaseOrderNumber")),
        new XElement("DATE", (DateTime)po.Attribute("OrderDate")),
        ConvertAddress(
            (from el in po.Elements("Address")
            where (string)el.Attribute("Type") == "Shipping"
            select el)
            .First()
        )
    );
    Console.WriteLine(newPo);
}

Function ConvertAddress(ByVal add As XElement) As IEnumerable(Of XElement)
    Dim fragment = New List(Of XElement)
    fragment.Add(<NAME><%= add.<Name>.Value %></NAME>)
    fragment.Add(<STREET><%= add.<Street>.Value %></STREET>)
    fragment.Add(<CITY><%= add.<City>.Value %></CITY>)
    fragment.Add(<ST><%= add.<State>.Value %></ST>)
    fragment.Add(<POSTALCODE><%= add.<Zip>.Value %></POSTALCODE>)
    fragment.Add(<COUNTRY><%= add.<Country>.Value %></COUNTRY>)
    Return fragment
End Function

Sub Main()
    Dim po As XElement = XElement.Load("PurchaseOrder.xml")
    Dim newPo As XElement = _
        <PO>
            <ID><%= po.@PurchaseOrderNumber %></ID>
            <DATE><%= CDate(po.@OrderDate) %></DATE>
            <%= _
                ConvertAddress( _
                (From el In po.<Address> _
                Where el.@Type = "Shipping" _
                Select el) _
                .First() _
                ) _
            %>
        </PO>
    Console.WriteLine(newPo)
End Sub

This example produces the following output:

<PO>
  <ID>99503</ID>
  <DATE>1999-10-20T00:00:00</DATE>
  <NAME>Ellen Adams</NAME>
  <STREET>123 Maple Street</STREET>
  <CITY>Mill Valley</CITY>
  <ST>CA</ST>
  <POSTALCODE>10999</POSTALCODE>
  <COUNTRY>USA</COUNTRY>
</PO>

See also