Develop Reference

Customizing an XML element using LINQ To XML

I have the following code:
XNamespace testNM = "urn:lst-emp:emp";
XDocument xDoc;
string path = "project_data.xml";
if (!File.Exists(path))
{
xDoc = new XDocument(
new XDeclaration("1.0", "UTF-16", null),
new XElement(testNM + "Test")
);
}
else
{
xDoc = XDocument.Load(path);
}
var element = new XElement("key",
new XElement("Type", type),
new XElement("Value", value));
xDoc.Element(testNM + "Test").Add(element);
// Save to Disk
xDoc.Save(path);
which produces an output in the XML file like this:
<?xml version="1.0" encoding="utf-16"?>
<Test xmlns="urn:lst-emp:emp">
<key xmlns="">
<Type>String</Type>
<Value>somestring</Value>
</key>
</Test>
How can I get an output like this in the XML file instead?
<?xml version="1.0" encoding="utf-16"?>
<Tests xmlns="urn:lst-emp:emp">
<key name="someString">
<Type>String</Type>
<Value>somestring</Value>
</key >
</Tests>
Note its only the 3rd line that has changed in the XML file.

You can do it this way:
var element = new XElement("key",
new XAttribute("name", "someString"),
new XElement("Type", "type"),
new XElement("Value", "value"));

To provide a complete version of Bilyukov's answer, this should produce the output expected. Obviously substitute the "someString" static string with a variable populated as you wish. Changes include using XName.Get(string, string) to create the appropriate XName objects for the XElement constructors.
XNamespace testNM = "urn:lst-emp:emp";
XDocument xDoc;
string path = "project_data.xml";
if (!File.Exists(path))
{
xDoc = new XDocument(
new XDeclaration("1.0", "UTF-16", null),
new XElement(XName.Get("Tests", testNM.NamespaceName))
);
}
else
{
xDoc = XDocument.Load(path);
}
var element = new XElement(XName.Get("key", testNM.NamespaceName),
new XAttribute("name", "someString"),
new XElement("Type", type),
new XElement("Value", value));
xDoc.Element(XName.Get("Tests", testNM.NamespaceName)).Add(element);
// Save to Disk
xDoc.Save(path);

Your XML has default namespace. Descendants of the element where default namespace declared is considered in the same default namespace, unless it is explicitly declared with different namespace. That's why you need to use the same XNamespace for <key> element. :
var element = new XElement(testNM +"key",
new XAttribute("name", "someString"),
new XElement(testNM +"Type", type),
new XElement(testNM +"Value", value));

How do I remove the xmlns="" attribute added to newly created XElement nodes?

When I add new nodes to the root of a node that has a namespace defined, subsequent nodes added all receive xmlns="" attached to to them. This is the code that shows my problem:
void Main()
{
var xdoc = new XDocument();
var shipmentRoot = new XElement("{someNS}Shipment");
var newElement = new XElement("ContainerCollection", new XElement("Container", new XElement("ContainerNumber", "42")));
newElement.SetAttributeValue("Content", "Partial");
shipmentRoot.Add(newElement);
xdoc.Add(shipmentRoot);
xdoc.Dump();
}
Generates this XML:
<Shipment xmlns="someNS">
<ContainerCollection Content="Partial" xmlns="">
<Container>
<ContainerNumber>42</ContainerNumber>
</Container>
</ContainerCollection>
</Shipment>
My desired XML would be:
<Shipment xmlns="someNS">
<ContainerCollection Content="Partial">
<Container>
<ContainerNumber>42</ContainerNumber>
</Container>
</ContainerCollection>
</Shipment>

While I suspect this is a duplicate, I can't easily find it. The problem is that in your desired XML, the ContainerCollection, Container and ContainerNumber elements are in the namespace "someNS" as that is the default inherited from their Shipment ancestor... but you're creating elements with an empty namespace. The fix is just to create them with the right namespace:
// I prefer this over using {someNS}Shipment, personally. YMMV.
XNamespace ns = "someNS";
var shipmentRoot = new XElement(ns + "Shipment");
var newElement = new XElement(ns + "ContainerCollection",
new XElement(ns + "Container",
new XElement(ns + "ContainerNumber", "42")));
newElement.SetAttributeValue("Content", "Partial");

How to specify an xmlns for XDocument?

I tried:
textBox1.Text = new XDocument(new XDeclaration("1.0", "UTF-8", "yes"),
new XElement("root1", new XAttribute( "xmlns", #"http://example.com"), new XElement("a", "b"))
).ToString();
But I get:
The prefix '' cannot be redefined from '' to 'http://example.com' within the same start element tag.
I also tried substituting (according to an answer I found) :
XAttribute(XNamespace.Xmlns,...
But got an error as well.
Note: I'm not trying to have more than one xmlns in the document.

The way the XDocument API works with namespace-scoped names is as XName instances. These are fairly easy to work with, as long as you accept that an XML name isn't just a string, but a scoped identifier. Here's how I do it:
var ns = XNamespace.Get("http://example.com");
var doc = new XDocument(new XDeclaration("1.0", "utf-8", null));
var root = new XElement(ns + "root1", new XElement(ns + "a", "b"));
doc.Add(root);
Result:
<root1 xmlns="http://example.com">
<a>b</a>
</root1>
Note the + operator is overloaded to accept an XNamespace and a String to result in and XName instance.

Linq to XML, C#

I have an xml in XDocument object (LINQ to XML). I need to add the namespace to each Xelement/node in the Xdocument.
I dont want to add in the below way. beceause i already have the xml in xdoc.
XDocument xDoc = new XDocument(
new XElement(ns + "root",
new XElement(ns + "person",
new XAttribute("id", 1),
new XElement(ns + "firstname", "jack"),
Below is the format i have
<root>
<person>1</person>
<firstname>jack</firstname>
</root>
I want to convert it to this below format
<emp:root>
<emp:person>1</emp:person>
<emp:firstname>jack</emp:firstname>
</emp:root>

foreach (var node in xDoc.Descendants())
{
node.Name = ns + node.Name.LocalName;
}
That should work:
Side note the namespace will only appear on the root node.

Create XML doc by LINQ, add xmlns,xmlns:xsi to it

I try to create an GPX XML document by LINQ to XML.
Everything works great, except adding xmlns, xmlns:xsi attributes to the doc. By trying it different way I get different exceptions.
My code:
XDocument xDoc = new XDocument(
new XDeclaration("1.0", "UTF-8", "no"),
new XElement("gpx",
new XAttribute("creator", "XML tester"),
new XAttribute("version","1.1"),
new XElement("wpt",
new XAttribute("lat","7.0"),
new XAttribute("lon","19.0"),
new XElement("name","test"),
new XElement("sym","Car"))
));
The output should also contain this:
xmlns="http://www.topografix.com/GPX/1/1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd"
How can I add it by Linq to XML? I tried several ways but it does not work, exceptions during compile time.

See How to: Control Namespace Prefixes. You could use code like this:
XNamespace ns = "http://www.topografix.com/GPX/1/1";
XNamespace xsiNs = "http://www.w3.org/2001/XMLSchema-instance";
XDocument xDoc = new XDocument(
new XDeclaration("1.0", "UTF-8", "no"),
new XElement(ns + "gpx",
new XAttribute(XNamespace.Xmlns + "xsi", xsiNs),
new XAttribute(xsiNs + "schemaLocation",
"http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd"),
new XAttribute("creator", "XML tester"),
new XAttribute("version","1.1"),
new XElement(ns + "wpt",
new XAttribute("lat","7.0"),
new XAttribute("lon","19.0"),
new XElement(ns + "name","test"),
new XElement(ns + "sym","Car"))
));
You have to specify the namespace for each element, because that's what using xmlns this way means.

From http://www.falconwebtech.com/post/2010/06/03/Adding-schemaLocation-attribute-to-XElement-in-LINQ-to-XML.aspx:
To generate the following root node and namespaces:
<root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:SchemaLocation="http://www.foo.bar someSchema.xsd"
xmlns="http://www.foo.bar" >
</root>
Use the following code:
XNamespace xsi = XNamespace.Get("http://www.w3.org/2001/XMLSchema-instance");
XNamespace defaultNamespace = XNamespace.Get("http://www.foo.bar");
XElement doc = new XElement(
new XElement(defaultNamespace + "root",
new XAttribute(XNamespace.Xmlns + "xsi", xsi.NamespaceName),
new XAttribute(xsi + "schemaLocation", "http://www.foo.bar someSchema.xsd")
)
);
Be aware - if you want to add elements to the document, you need to specify the defaultNamespace in the element name or you will get xmlns="" added to your element. For example, to add a child element "count" to the above document, use:
xdoc.Add(new XElement(defaultNamespace + "count", 0)