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.
Related
I'm familiar with these two methods:
var newDataSet = XmlSerializer.DeserializeFromString<NEWDATASET>(xmlDoc.OuterXml);
var newDataSet = xmlDoc.OuterXml.FromXml<NEWDATASET>();
But they both give me the same error:
DeserializeDataContract: Error converting type: Error in line 1
position 40. Expecting element 'NEWDATASET' from namespace
''.. Encountered 'Element' with name 'NEWDATASET',
namespace ''.
I feel like there should be a way to get this to work as long as the the element names either match the public property names or the DataMemberAttribute Name parameter of the public property was set to the element name.
ServiceStack doesn't have it's own XML Serializer, it's DataContractSerializer uses .NET's XML DataContract and its XmlSerializer uses .NET's XmlSerializer. So the XML payload would need to be deserialized from either of those BCL implementations.
An alternative way to parse arbitrary XML is to use XLinq and ServiceStack's XLinqExtensions which provide UX-friendly helpers to simplify XML parsing.
Here are some examples for parsing arbitrary XML with XLinq and helpers:
XlinqExtensionsTests.cs
Parsing Razor Namespaces from Web.config
Parsing RSA Private Key
Summary
When using the XmlSerializer class, serializing a List<T> (where T can be serialized with XmlSerializer without problems) using XmlAttributeOverrides such as this:
using xmls = System.Xml.Serialization;
...
xmls.XmlAttributeOverrides attributeOverrides = new xmls.XmlAttributeOverrides();
attributeOverrides.Add(typeof(T), new xmls.XmlAttributes()
{
XmlRoot = new xmls.XmlRootAttribute("foo")
});
attributeOverrides.Add(typeof(List<T>), new xmls.XmlAttributes()
{
XmlArray = new xmls.XmlArrayAttribute("foobar"),
XmlArrayItems = { new xmls.XmlArrayItemAttribute("foo") },
});
will throw the following InvalidOperationExcpetion at the inner-most exception:
System.InvalidOperationException: XmlRoot and XmlType attributes may not be specified for the type System.Collections.Generic.List`1[[T, programname, Version=versionnumber, Culture=neutral, PublicKeyToken=null]].
What I expect from the serializer
<texparams>
<texparam pname="TextureMinFilter" value="9729"/>
<texparam pname="TextureMagFilter" value="9729"/>
</texparams>
What I can sucessfully get at the moment
<ArrayOfTextureParameter xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<TextureParameter pname="TextureMinFilter" value="9729" />
<TextureParameter pname="TextureMagFilter" value="9728" />
</ArrayOfTextureParameter>
Background Info
I have been messing around with XML Serialization lately but have come across a problem. I am trying to serialize and deserialize some classes that wrap OpenGL textures.
In one of my classes (which I appropriately called BitmapTexture2d) I have a Bitmap field, which I wish to store in a Base64 element like so:
<bitmap64>
*base64goeshere*
</bitmap64>
Since I want to keep my code as neat as possible I decided to use the IXmlSerializable interface instead of creating a property which can convert a string and a Bitmap back and forth.
Later on in the process I decided to use the XmlSerializer class to generate the XML for a single field defined in Texture2d (which BitmapTexture2d is derived from) called Parameters (which is a List<TextureParameter> and TextureParameter is serializable by the XmlSerialization class). However this is how the serializer defaulted to serializing the List<TextureParameter>:
<ArrayOfTextureParameter xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<TextureParameter pname="TextureMinFilter" value="9729" />
<TextureParameter pname="TextureMagFilter" value="9728" />
</ArrayOfTextureParameter>
After seeing this, I decided to try and change the names of the nodes. After some research (where I landed at stackoverflow multiple times) I discovered the XmlAttributeOverrides class which can be passed to the constructor of XmlSerializer to add/override node names etc.
After writing out my code, the constructor for the sub-serializer started throwing an exception as described above. I have tried using an array which threw the same exception. I later though to serialize each element in the list one by one, but came to the conclusion that it was harder than I thought to achieve it that way. I posted this question somewhere else with no answer. And here I am...
Your problem is that you are trying to use overrides to attach [XmlArray] and [XmlArrayItem] to the type List<T>. However, as shown in the docs, [XmlArray] cannot be used in this manner:
[AttributeUsageAttribute(AttributeTargets.Property | AttributeTargets.Field
| AttributeTargets.Parameter | AttributeTargets.ReturnValue,
AllowMultiple = false)]
public class XmlArrayAttribute : Attribute
Notice there is no AttributeTargets.Class included? That means that [XmlArray] cannot be applied directly to a type and so attempting to do so via XML overrides rightly throws an exception.
But as to why that exception message states,
System.InvalidOperationException: XmlRoot and XmlType attributes may not be specified for the type System.Collections.Generic.List`1...
Er, well, that message is simply wrong. It would appear to be a minor bug in XmlSerializer. You could even report it to Microsoft if you want.
What you need to do instead is:
Override the [XmlRoot] attribute of List<T> to specify the desired name, in this case "texparams", AND
Override the [XmlType] attribute of T and set XmlTypeAttribute.TypeName to be the desired collection element name. In the absence of an [XmlArrayItem(name)] override this is what controls the element names of collections whose items are of type T.
Thus your code should look like:
static XmlSerializer MakeListSerializer<T>(string rootName, string elementName)
{
xmls.XmlAttributeOverrides attributeOverrides = new xmls.XmlAttributeOverrides();
attributeOverrides.Add(typeof(List<T>), new xmls.XmlAttributes()
{
XmlRoot = new xmls.XmlRootAttribute(rootName),
});
attributeOverrides.Add(typeof(T), new xmls.XmlAttributes()
{
XmlType = new xmls.XmlTypeAttribute(elementName),
});
return new XmlSerializer(typeof(List<T>), attributeOverrides);
}
Sample fiddle.
Note that when constructing an XmlSerializer using XmlAttributeOverrides you must cache the serializer for later reuse to avoid a severe memory leak, for reasons explained here.
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.
I'm generating objects and class es from XSD files. But the classes created under one namespace and not with the target namespace of the XSD.
How can I compile the schema, and the class should be generated under the namespace?
Here is my code fore example:
// generate an assembly representing the given schema:
var codeNamespace = new CodeNamespace(namespaceName);
var codeProvider = new CSharpCodeProvider();
var codeGenerationOptions = new CodeGeneratorOptions();
using (var writer = new StringWriter())
{
codeProvider.GenerateCodeFromNamespace(codeNamespace, writer,
codeGenerationOptions);
code = writer.ToString();
}
Your code example works in that it puts the generated code in the namespace you specify in your namespaceName variable. If you want your namespace to match the XSD, you can set your namespaceName variable accordingly.
For example, if I define string namespaceName = "My.Namespace.One"; in your example code, the resulting value of code is "namespace My.Namespace.One {\r\n\r\n}" as expected.
Thus you would simply need to read the namespace from your XSD and assign it to namespaceName If your issue is that you are wanting to use multiple namespaces, then the issue is related to how you process the XSD for code generation, which is not shown at all in your example.
However to actually compile the code you generate, the namespace will need to conform to C# limitations. A namespace like http://schemas.microsoft.com/winfx/2006/xaml would not compile in C#. That namespace may (I'm not sure) be valid at the IL byte code level, but even if it is I would really wonder if what you are doing is worth expending that sort of effort, especially considering it would be a pain for C# to use the generated assembly.
I have the feeling that some details may be missing from your question/example and this may not be the info you are looking for; however, I believe this answer is consistent with what you have provided.
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.