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Using default namespace with System.Xml.Linq.XAttribute explained. #44501

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19 changes: 14 additions & 5 deletions docs/standard/linq/create-document-namespaces-csharp.md
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
---
title: How to create a document with namespaces in C# - LINQ to XML
description: Use the XNamespace object in C# to create documents that have default namespaces or namespaces with a prefix.
ms.date: 07/20/2015
ms.date: 01/23/2025
ms.topic: how-to
---

Expand Down Expand Up @@ -60,6 +60,8 @@ The following example shows the creation of a document that contains two namespa

By including namespace attributes in the root element, the namespaces are serialized so that `http://www.adventure-works.com` is the default namespace, and `www.fourthcoffee.com` is serialized with a prefix of `fc`. To create an attribute that declares a default namespace, you create an attribute with the name `xmlns`, without a namespace. The value of the attribute is the default namespace URI.

If a default namespace declaration is in scope, it applies to child `XElement` objects by prefixing their local names with the corresponding `XNamespace` object. On the other hand, default namespace declarations do not apply directly to attribute names. So, `XAttribute` objects in the default namespace are defined by *not* prefixing their local name with the corresponding `XNamespace` object.

```csharp
// The http://www.adventure-works.com namespace is forced to be the default namespace.
XNamespace aw = "http://www.adventure-works.com";
Expand All @@ -70,8 +72,14 @@ XElement root = new XElement(aw + "Root",
new XElement(fc + "Child",
new XElement(aw + "DifferentChild", "other content")
),
new XElement(aw + "Child2", "c2 content"),
new XElement(fc + "Child3", "c3 content")
new XElement(aw + "Child2", "c2 content",
new XAttribute("DefaultNs", "default namespace"),
new XAttribute(fc + "PrefixedNs", "prefixed namespace")
),
new XElement(fc + "Child3", "c3 content",
new XAttribute("DefaultNs", "default namespace"),
new XAttribute(fc + "PrefixedNs", "prefixed namespace")
)
);
Console.WriteLine(root);
```
Expand All @@ -83,8 +91,9 @@ This example produces the following output:
<fc:Child>
<DifferentChild>other content</DifferentChild>
</fc:Child>
<Child2>c2 content</Child2>
<fc:Child3>c3 content</fc:Child3>
<Child2 DefaultNs="default namespace" fc:PrefixedNs="prefixed namespace">c2 content</Child2>
<fc:Child3 DefaultNs="default namespace" fc:PrefixedNs="prefixed namespace">c3 content</fc:Child3>

</Root>
```

Expand Down
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