Reputation: 31
Is there a way in Linq to use two prefixes for the same namespace? Example, I have two prefixes below "foo1" and "foo2" pointing to the same namespace that I want to use in my document. How do I do that?
<foo1:Begin foo2:Name="somevalue" xmlns:foo1="http://foo" xmlns:foo2="http://foo" xmlns="http://bar">
<foo1:Child foo2:Name="somename" />
<SomeBarElement />
</foo1:Begin>
In all my code I define the elements as:
string foo = "http://foo";
string bar = "http://bar";
string foo1 = "foo1";
string foo2 = "foo2";
XName Begin = "{" + foo + "}" + "Begin";
XName Child = "{" + foo + "}" + "Child";
XName Name = "{" + foo + "}" + "Name";
XName SomeBarElement = "{" + bar + "}" + "SomeBarElement";
I would like to be able to use a similar definition and usuage of elements to maintain consistency. And wherever I dont have two prefixes I do something like:
XElement doc = new XElement(Begin,
new XAttribute(XNamespace.Xmlns + foo1, foo),
new XAttribute(XNamespace.Xmlns, bar),
new XElement(Child, new XAttribute(Name, "somename")),
new XElement(SomeBarElement)
);
I need two prefixes since the namespaces may change later - and even if not, it makes sense to logically separate the elements using different prefixes.
Upvotes: 3
Views: 890
Reputation: 8049
You actually can control the prefixes used by LINQ to Xml - but not when you have more than one prefix mapping to a namespace.
I have a post about how to do it here: How to Control Namespace Prefixes with LINQ to Xml. I'll include some of the highlights below. Before that, it's important to know why you can't logically separate elements or attributes using the same namespace.
The TL;DR is:
So if "...logically separating the elements" is important, then the way to do that is by using distinct namespaces for each logical unit. You could do this by creating a namespaces like so:
XNamespace nsParent1 = "http://foo";
XNamespace nsChild1OfParent1 = "http://foo/1";
XNamespace nsChild2OfParent1 = "http://foo/2";
XNamespace nsParent2 = "http://bar";
XNamespace nsChild1OfParent2 = "http://bar/1";
and use whatever naming convention makes sense to you.
Now, the details:
This old MSDN article, though it's from 2001, still applies. This excerpt describes how namespaces should be handled:
A namespace is a set of names in which all names are unique. For example, the names of my children could be thought of as a namespace, as could the names of California corporations, the names of C++ type identifiers, or the names of Internet domains. Any logically related set of names in which each name must be unique is a namespace.
Namespaces make it easier to come up with unique names. Imagine how hard it would be to name your next child if the name had to be unique across the face of the earth. Restricting uniqueness to a more limited context, like my set of children, simplifies things tremendously. When I name my next child, my only consideration is that I don't use the same name that I already used for one of my other children. Another set of parents can choose the same name I choose for one of their children, but those names will be part of distinct namespaces and, therefore, can be easily distinguished.
Before a new name is added to a namespace, a namespace authority must ensure that the new name doesn't already exist in the namespace. In some scenarios this is trivial as it is in child naming. In others it's quite complex. Today's many Internet naming authorities present a good example. If this step is skipped, however, duplicate names will eventually corrupt the namespace, making it impossible to refer to certain names without ambiguity. When this happens, the set of names is no longer officially considered a namespace—by definition a namespace must ensure the uniqueness of its members.
The "traditional" XML DOM represented by classes in the System.Xml
namespace does not only maintain information about the prefix for the XmlElement
and XmlAttribute
instances thru the XmlElement.Prefix
and XmlAttribute.Prefix
properties. But these properties are also writable so you could modify them as you see fit.
However, LINQ to Xml adheres to specification that the Namespace Names should be unique. Note that this doesn't stop you from parsing or using XML that uses multiple names for the same namespace. LINQ to Xml does not maintain any prefix information in either XElement
or XAttribute
. It considers the most important part of the namespace to be the uri itself, not the prefix.
Using your code:
var bar = XNamespace.Get("http://bar");
var foo1 = XNamespace.Get("http://foo");
var foo2 = XNamespace.Get("http://foo");
var x = new XElement(foo1 + "begin",
new XAttribute(foo2 + "Name", "somevalue"),
new XElement("child", new XAttribute(foo2 + "Name", "somevalue")),
new XElement(bar + "barElement"));
Console.WriteLine(x.ToString());
the serialized output is:
<begin p1:Name="somevalue" xmlns:p1="http://foo" xmlns="http://foo">
<child p1:Name="somevalue" xmlns="" />
<barElement xmlns="http://bar" />
</begin>
So here's how to control them:
// add the 'xmlns' namespace declarations for your prefixes
x.Add(
new XAttribute(XNamespace.Xmlns + "foo", foo1),
new XAttribute(XNamespace.Xmlns + "bar", bar));
Now the serialized output is:
<foo:begin foo:Name="somevalue" xmlns:foo="http://foo" xmlns:bar="http://bar">
<child foo:Name="somevalue" />
<bar:barElement />
</foo:begin>
Upvotes: 0
Reputation: 28728
Yes, you can use two prefixes for the same namespace. You'd do this by using two namespaces with the same value.
var bar = XNamespace.Get("http://bar");
var foo1 = XNamespace.Get("http://foo");
var foo2 = XNamespace.Get("http://foo");
var x = new XElement(foo1 + "begin",
new XAttribute(foo2 + "Name", "somevalue"),
new XElement("child", new XAttribute(foo2 + "Name", "somevalue")),
new XElement(bar + "barElement"));
But you cannot control XML namespace prefixes using LINQ-to-XML; and you should not need to control namespace prefixes.
This XML renders as
<begin p1:Name="somevalue" xmlns:p1="http://foo" xmlns="http://foo">
<child p1:Name="somevalue" xmlns="" />
<barElement xmlns="http://bar" />
</begin>
As you can see, you have three namespaces and both xmlns
and xmlns:p1
refer to your http://foo
URI. But there's no way to tell LINQ-to-XML that it should use prefixes like foo1
, foo2
etc.
Trying to fiddle with XML namespace prefixes is unecessary hacking. Your code should not depend on concrete prefxies - they should be determined at parse time by reading the XML document itself.
Upvotes: 1