I need to produce an xml document where all elements and attributes are prefixed with (the same) namespace (I know this is not ideal, but unfortunately is needed for interoperation with InfoPath). Using the .NET XmlSerializer, initialized with the right namepsace and prefix, I generally have no problem generating prefixed xml:
xmlSerializer = new XmlSerializer(typeof(T));
xmlNamespaces = new XmlSerializerNamespaces();
xmlNamespaces.Add("foo", "www.namespace.com");
...
[XmlRoot(Namespace = "www.namespace.com")]
public class label
{
[XmlAttribute(Namespace = "www.namespace.com")]
public string id { get; set; }
[XmlElement(Namespace = "www.namespace.com")]
public string text { get; set; }
}
This generates xml
<foo:label id="0" xmlns:foo="www.namespace.com">
<foo:text>content</foo:text>
</foo:label>
The problem is this: the prefix is applied to everything, except the "id" attribute in the same namespace.
I thought this might be behavior prescribed by W3C, and that attributes declared as belonging to a prefixed element would inherit that prefix. However, it seems that attributes that do not have an associated namespace/prefix do not behave like this - see XML namespaces and attributes and here, which states:
"An attribute never inherits the namespace of its parent element. For that reason an attribute is only in a namespace if it has a proper namespace prefix"
In this case, shouldn't the serializer generate a prefix to show the attribute is in that namespace? Or is this not correct?
Thanks in advance!
MORE INFO: Further investigation (see SamuelNeff's answer below) has determined that unprefixed attributes do not inherit the namespace of their containing element. Does this mean the XmlSerializer is producing off-spec attributes? Is there a way to force it to add the prefix? It will add a prefix if a different namespace uri is added in the XmlAttribute attribute.
OOPS: My interpretation of spec is wrong. This incorrect response is marked as the answer, so I can't delete it. Sorry.
Attributes without prefixes are in the same namespace as their containing element. You only need to apply a prefix to an attribute if the attribute has a namespace different from its element.
Default namespace declarations do not apply directly to attribute names; the interpretation of unprefixed attributes is determined by the element on which they appear.
http://www.w3.org/TR/2009/REC-xml-names-20091208/#defaulting
Try using the Prefix property?
XmlAttribute Prefix on MSDN
This is a rather odd problem, also setting the Prefix and NamespaceURI manually is probably error prone. Are you sure the namespace on the attribute is even necessary? While it may not be to spec, the client or server you are working with should skip the containing element of the attribute if it is in your foo namespace right? At which point why would it care what namespace your attribute has.
Related
I'm expecting XML output as follows:
<MyBase type="MyDerived"
xmlns="http://www.mynamespace.com/MySchema" />
Instead, my actual output is as follows:
<MyBase i:type="MyDerived"
xmlns="http://www.mynamespace.com/MySchema"
xmlns:i="http://www.w3.org/2001/XMLSchema-instance" />
I'm using the following class definitions to attempt to generate my expected output:
MyBase.cs
namespace MyProject
{
[KnownType(typeof(MyDerived))]
[DataContract(Namespace = MyBase.Namespace)]
public abstract class MyBase
{
public const string Namespace = "http://www.mynamespace.com/MySchema";
}
}
MyDerived.cs
namespace MyProject.Events
{
[DataContract(Namespace = MyBase.Namespace)]
public sealed class MyDerived : MyBase {}
}
And I'm using the following serialization code:
var knownTypes = new Type[]
{
typeof(MyDerived)
};
var xmlDictionary = new XmlDictionary(1);
var settings = new DataContractSerializerSettings();
settings.KnownTypes = knownTypes;
settings.RootNamespace = xmlDictionary.Add(MyBase.Namespace);
serializer = new DataContractSerializer(typeof(MyBase), settings);
var actual = String.Empty;
using (var memoryStream = new MemoryStream())
{
serializer.WriteObject(memoryStream, new MyDerived());
memoryStream.Position = 0;
using (var streamReader = new StreamReader(memoryStream))
{
actual = streamReader.ReadToEnd();
}
}
I'm not sure why it's using the XMLSchema-instance namespace for my derived object instead of the namespace I've specified to use. I've spent over an hour digging around StackOverflow, Google, and MSDN trying to figure out what I'm doing wrong, but I must be missing it. It seems so close, it must be a simple mistake.
Is this a problem with my class structure, or am I misapplying attributes in some way?
How can I get my expected output?
You may just be misreading the XML and things are working as desired. In your XML, the namespace xmlns:i="http://www.w3.org/2001/XMLSchema-instance" is only being used to qualify the attribute i:type, and nothing else. All of your actual data is in the namespace you specify. If the object itself were in a different namespace, you would see something like:
i:type="i:MyDerived"
But you're not.
http://www.w3.org/2001/XMLSchema-instance is a W3C globally standard namespace, knowledge of which is built in to DataContractSerializer (as well as many other XML serializers). It contains 4 built-in attributes defined as follows in the standards document:
nil: Signals that an element may be ·valid· without content if it has this attribute with the value true.
schemaLocation and noNamespaceSchemaLocation: used to provide hints as to the physical location of schema documents.
type: An element information item in an instance may explicitly assert its type using the attribute type. The value of this attribute is a ·QName·.
The i:type you are seeing is the last of these standard, globally recognized attributes. It says: "this element has the following type". Reasons for DataContractSerializer to use it to represent .Net type information could include:
It is standard. For instance XmlSerializer recognizes and supports the same attribute.
Your element might have its own data attribute named type. If so, it would reside in its own namespace, not http://www.w3.org/2001/XMLSchema-instance. The latter is reserved by convention for schema information not content, thereby avoiding name collision.
For more, see Understanding Known Types and Data Contract Known Types.
Unfortunately you'll not be able to achieve it even using custom XmlWriter. DataContractSerializer doesn't work like XMLSerializer. The information into your xml is added to support the fact:
The line xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" tells the XML parser that this document should be validated against a schema.
Also these namespaces are considered as reserved namespaces. So if you try to override them .Net runtime will throw exception.
#dbc explained it very well and inclusion of the namespaces is part of a pretty standard process and is harmless for your xml.
If you really need to get rid of this default namespace then you just have to hack your XML output with string replace method. But this may lead you to problems while desalinizing.
I have an XPath query which looks right to me, but isn't returning any results.
The XML document it's being tested against:
<Deployment xmlns="http://schemas.microsoft.com/client/2007/deployment" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
<Deployment.Parts>
<AssemblyPart x:Name="foo" Source="foo.dll" />
</Deployment.Parts>
</Deployment>
The code:
Xml = new XmlDocument();
Xml.LoadXml(text);
Manager = new XmlNamespaceManager(Xml.NameTable);
//use constants for namespaces to make more readable
Manager.AddNamespace("a", NS_DEPLOYMENT_2007); //use 'a' for default namespace here so xpath is easier
Manager.AddNamespace("x", NS_XAML_2006);
string xpath="//a:Deployment.Parts/a:AssemblyPart[#a:Source='foo.dll']";
var tmp = Xml.SelectNodes(xpath, Manager);
What is wrong with my XPath query here?
You need to remove the namespace prefix from your attribute:
string xpath="//a:Deployment.Parts/a:AssemblyPart[#Source='foo.dll']";
You only need to specify the namespace for the attribute if it explicitly has a namespace defined, so when you would want to query the Name attribute, you would have to add it:
string xpath="//a:Deployment.Parts/a:AssemblyPart[#x:Name='foo']";
I suspect this part is your problem:
#a:Source='foo.dll'
Unlike element names, attribute names don't inherit a namespace. Your document doesn't specify a namespace for the attribute, so I don't think you should do so either.
Try just:
#Source='foo.dll'
(As an aside, I would personally use LINQ to XML instead of XPath - I find it generally simpler. YMMV, but it may be worth considering - if you're using .NET 3.5 or higher, of course.)
From "Namespaces in XML 1.0 (3rd edition)" section 6.2 (emphasis mine):
The scope of a default namespace declaration extends from the beginning of the start-tag in which it appears to the end of the corresponding end-tag, excluding the scope of any inner default namespace declarations. In the case of an empty tag, the scope is the tag itself.
A default namespace declaration applies to all unprefixed element names within its scope. Default namespace declarations do not apply directly to attribute names; the interpretation of unprefixed attributes is determined by the element on which they appear.
Suppose I have such elements in my XML document:
<xs:appinfo>
<CustomXML>
<Something>something</Something>
</CustomXML>
</xs:appinfo>
"xs" is declared as the default schema namespace. My question is: how would a parser interpret the inner elements of xs:appinfo? In which namespace do they belong?
I ask because I'm parsing the code in C# and it keeps adding "xmlns="" " to the CustomXML element, which makes me assume that otherwise it'd treat these elements as schema elements.
According to §6.2 Namespace Defaulting of Namespaces in XML 1.0 (Third Edition):
The scope of a default namespace declaration extends from the beginning of the start-tag in which it appears to the end of the corresponding end-tag, excluding the scope of any inner default namespace declarations. […]
A default namespace declaration applies to all unprefixed element names within its scope.
That means that elements with no namespace prefix are interpreted as being in the default namespace. Default namespace is usually defined on the first element of the document and look like this:
<element xmlns="namespace-uri">
The library redefines the default namespace when it's necessary, that is, when you add an element to the document with no namespace. In other words, such element is not in the default namespace, so the library solves this by adding xmlns="" to that element, which redefined the default namespace for this element and all its descendants to "no namespace".
If you want to add element that is in the default namespace, you have to specify it explicitly. For example, in LINQ to XML:
XDocument doc = …;
var ns = doc.Root.GetDefaultNamespace();
var newElement = new XElement(ns + "foo"));
I'm having trouble deserializing XML with an "undefined" namespace prefix which really is defined.
We've published an internal web service in C# which serves a variety of clients. A new client's IDE insists on declaring xsi:type for every element in its XML output, and they can't turn off this "feature".
The XML message they produce goes like this, where "namespace" is the correct namespace.
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<myOperation xsi:type="ns1:namespace" xmlns="namespace" xmlns:ns1="namespace">
<inputString xsi:type="xsd:string">ABCDEF</inputString>
<books xsi:type="ns1:booksType">
<bookID xsi:type="xsd:string">ABC123</bookID>
<bookID xsi:type="xsd:string">DEF456</bookID>
</books>
<!-- ... snip... -->
</myOperation>
</soapenv:Body>
<books> is basically an array of strings.
The service method accepts as XmlNode, but XmlSerializer throws a "prefix 'ns1' not defined" error. (It is defined in a parent node, but apparently that is not good enough.) I have a similar problem using wsdl.exe to generate classes and deserialize the input for me.
Using XmlNamespaceManager to specify prefixes doesn't seem right -- akin to magic numbers, and I can't predict which prefix a given consumer will declare anyway. Is there a way to handle this without stripping the attributes out (books.Attributes.RemoveAll)? That doesn't feel particularly elegant either.
I've found that books.OuterXML does not contain any information for 'ns1' unless I hack the element inbound to use that prefix (), so I can see why it complains, but I don't yet understand why 'ns1' isn't recognized from its previous definition above.
Many thanks for any help, or at least education, someone can provide.
Edits: it works fine if I change <books> to use the prefix, i.e. <ns1:books xsi:type="ns1:booksType">. This works whether I've defined xmlns or no. That may be consistent with this answer, but I still don't see how I would feasibly declare the prefix in the service code.
#Chris, certainly. Hope I can strike a balance between "stingy with closed source" and "usable for those who would help". Here "books" is the XmlNode received in the service method parameter. (Not to get off topic, but will also humbly take suggestions to improve it in general; I'm still a novice.)
XmlSerializer xmlSerializer = new XmlSerializer(typeof(booksType));
StringReader xmlDataReader = new StringReader(books.OuterXml);
books = (booksType)xmlSerializer.Deserialize(xmlDataReader);
The class is pretty much this:
[Serializable()]
[XmlRoot("books", Namespace = "namespace")]
[XmlTypeAttribute(TypeName = "booksType", Namespace = "namespace")]
public class booksType
{
[XmlElement(ElementName = "bookID")]
public string[] bookIDs { get; set; }
}
Your deserialization code could look something like this:
XmlSerializer sz = new XmlSerializer(typeof(booksType));
var reader = new XmlNodeReader(booksXmlNode);
var books = sz.Deserialize(reader);
[EDIT] This is better, because the namespace declarations are preserved with the XmlNode, whereas converting to an XML string via OuterXml appears to slice off the namespace declaration for the ns1 prefix, and the serializer then barfs on the type attribute value containing this prefix. I imagine this is a bug in the XML implementation but maybe an XML guru can confirm this.
This should get you past the error you are seeing, but whether it solves the problem completely I'm not sure.
[FURTHER EDIT] As noted in the comments below, there is a bug in the .NET XmlSerializer which is causing the deserialization to fail. Stepping through the deserialization code in the generated assembly, there is a point where the following condition is tested:
(object) ((System.Xml.XmlQualifiedName)xsiType).Namespace == (object)id2_namespace))
Although the Namespace property of the XmlQualifiedName has the same value ('namespace') as the string variable id2_namespace, the condition is evaluating to false because it is coded as an object identity test rather than a test for string value equivalence. Failing this condition leads directly to the exception reported by OP.
As far as I can see, this bug will always cause deserialization to fail whenever the XML for the object being deserialized uses one prefix on the object's root element name, and another prefix (defined as the same namespace) on that element's xsi:type attribute.
The Xml response I receive is as follows:
<response>
<item xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="java:com.someDomain.item">
<name>some name</disc-name>
<description>some description</disc-desc>
</item>
<item xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="java:com.someDomain.item">
<name>some name</disc-name>
<description>some description</disc-desc>
</item>
<otherValue>12.1</otherValue>
</response>
My class is decorated as such:
[XmlElement("item")]
public Item[] Items{get;set;}
[XmlElement("otherValue")
public string OtherValue{get;set;}
When I attempt to deserialize the above Xml to the class described, I receive an error of "Namespace prefix 'java' is not defined". Adding the "namespace" attribute to the class resolves the parsing error(however, the xml is then distorted from the original).
ie
[XmlElement(ElementName="item",Namespace="java")]
How should I be decorating a given property to match up with a new namespace? Or, how do I correctly define the namespace?
I'm not 100% on using a stock array for my enumerable section either, but I think the namespace issue takes precident at the moment. Any insight or thoughts are greatly appreciated!
UPDATE:
I think the question is better rephrased now that I've gone back and forth a bit:
How do you use an XmlElementAttribute(or other attribute) to have a class that can serialize into the item snippet above, including the xsi tags?
As for my particular problem, I've realized since the Xml response is out of my control, I don't need the xsi attributes to begin with. To workaround the serialization issue, I'm simply doing the following(XmlElement element contains the original document above):
foreach(XmlNode node in element)
node.Attributes.RemoveAll();
I'm only noting my personal workaround as this is not actually a solution.
You were right the first time. "java" is not a namespace. It's a namespace prefix. That's an abbreviation of the namespace, for use in the XML. Otherwise, the actual namespace would need to be repeated wherever you currently see "java:".
You can use List<Item> instead of Item[].
Unfortunately this is valid XML, and completely conforms to the XML Standard.
It validates, it's correct and it's complete.
The problem you're having is in the deserialization, which is not a part of the XML Standard and is related to how .NET maps declared XML types to internal CLR types.
The xsi:type is a namespace reference and is intended to allow XML documents to substitute a derived type from another namespace for the declared type in the schema.
I know from my own experience that coders tend to react in shock that this sort of thing is even legal, much less correct XML. It basically hijacks your schema.
You do not need even need to include the foreign namespace in order for this to be considered correct.
(see this article for more ranting on this subject: http://norman.walsh.name/2004/01/29/trainwreck)
Now, as to how to handle your stated problem: deserialize this mess.
1) process the xml text and remove the xsi-types declaration and hope there are no fields declared that extend the base type.
2) declare a type that derives from your base type in the schema.
This looks like the following:
// note this "XmlIncludeAttribute" references the derived type.
// note that in .NET they are in the same namespace, but in XML they are in different namespaces.
[System.Xml.Serialization.XmlIncludeAttribute(typeof(DerivedType))]
[System.SerializableAttribute()]
[System.Xml.Serialization.XmlTypeAttribute(Namespace="http://BaseNameSpace")]
[System.Xml.Serialization.XmlRootAttribute(Namespace="http://BaseNameSpace", IsNullable=true)]
public partial class MyBaseType : object
{
...
}
/// <remarks/>
[System.SerializableAttribute()]
[System.Xml.Serialization.XmlTypeAttribute(Namespace="http://DerivedNameSpace")]
[System.Xml.Serialization.XmlRootAttribute(Namespace="http://DerivedNameSpace", IsNullable=true)]
public partial class DerivedType: MyBaseType
{
...
}
This is only a rough outline, hopefully enough to get you started. Note that this is not an easy problem to solve progmatically because it's always possible for someone to feed you XML and it will validate but not deserialize properly.