I'm reverse engineering a file format that stores each field as TLV blocks (type, length, value).
The fields do not have to be in order, or even present at all. Their presence is denoted with a sentinel, which is a 16-bit type identifier and a 32-bit end offset. There are hundreds of unique identifiers, but a decent chunk of those are just single primitive values. aside from denoting the type, they can also identify what field the data should be stored in.
It is also worth noting that there will never be a duplicate id on a parent structure. The only time is can occur is if there are multiple of the same object type in an array/list.
I have successfully written a Kaitai definition for one of them:
meta:
id: struct_02ea
endian: le
seq:
- id: unk_00
type: s4
- id: fields
type: field_block
repeat: eos
types:
sentinel:
seq:
- id: id
type: u2
- id: end_offset
type: u4
field_block:
seq:
- id: sentinel
type: sentinel
- id: value
type:
switch-on: sentinel.id
cases:
0xF0: u1
0xF1: u1
0xF2: u1
0xF3: u1
0xF4: u4
0xF5: u4
size: sentinel.end_offset - _root._io.pos
Handling things this way does work, and I could likely map out the entire format like this. However, when it comes time to compiling this definition into another format, things get nasty.
Since I am wrapping each field in a field_block, the generated code stores these values in that type of object. This is incredibly inefficient when half of the generated field_block objects store a single integer. It would also require the consuming code to iterate through a list of each field block in order to get the actual field's value.
Ideally, I would like to define this structure so that the sentinels are only parsed while Kaitai is reading the data, and each value would be mapped to a field on the parent structure.
Is this possible? This technology is really cool, and I'd love to use it in my project, but I feel like the overhead that this is generating is a lot more trouble than it's worth.
Here's an example of the definition when compiled into C#:
using System.Collections.Generic;
namespace Kaitai
{
public partial class Struct02ea : KaitaiStruct
{
public static Struct02ea FromFile(string fileName)
{
return new Struct02ea(new KaitaiStream(fileName));
}
public Struct02ea(KaitaiStream p__io, KaitaiStruct p__parent = null, Struct02ea p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root ?? this;
_read();
}
private void _read()
{
_unk00 = m_io.ReadS4le();
_fields = new List<FieldBlock>();
{
var i = 0;
while (!m_io.IsEof) {
_fields.Add(new FieldBlock(m_io, this, m_root));
i++;
}
}
}
public partial class Sentinel : KaitaiStruct
{
public static Sentinel FromFile(string fileName)
{
return new Sentinel(new KaitaiStream(fileName));
}
public Sentinel(KaitaiStream p__io, Struct02ea.FieldBlock p__parent = null, Struct02ea p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root;
_read();
}
private void _read()
{
_id = m_io.ReadU2le();
_endOffset = m_io.ReadU4le();
}
private ushort _id;
private uint _endOffset;
private Struct02ea m_root;
private Struct02ea.FieldBlock m_parent;
public ushort Id { get { return _id; } }
public uint EndOffset { get { return _endOffset; } }
public Struct02ea M_Root { get { return m_root; } }
public Struct02ea.FieldBlock M_Parent { get { return m_parent; } }
}
public partial class FieldBlock : KaitaiStruct
{
public static FieldBlock FromFile(string fileName)
{
return new FieldBlock(new KaitaiStream(fileName));
}
public FieldBlock(KaitaiStream p__io, Struct02ea p__parent = null, Struct02ea p__root = null) : base(p__io)
{
m_parent = p__parent;
m_root = p__root;
_read();
}
private void _read()
{
_sentinel = new Sentinel(m_io, this, m_root);
switch (Sentinel.Id) {
case 243: {
_value = m_io.ReadU1();
break;
}
case 244: {
_value = m_io.ReadU4le();
break;
}
case 245: {
_value = m_io.ReadU4le();
break;
}
case 241: {
_value = m_io.ReadU1();
break;
}
case 240: {
_value = m_io.ReadU1();
break;
}
case 242: {
_value = m_io.ReadU1();
break;
}
default: {
_value = m_io.ReadBytes((Sentinel.EndOffset - M_Root.M_Io.Pos));
break;
}
}
}
private Sentinel _sentinel;
private object _value;
private Struct02ea m_root;
private Struct02ea m_parent;
public Sentinel Sentinel { get { return _sentinel; } }
public object Value { get { return _value; } }
public Struct02ea M_Root { get { return m_root; } }
public Struct02ea M_Parent { get { return m_parent; } }
}
private int _unk00;
private List<FieldBlock> _fields;
private Struct02ea m_root;
private KaitaiStruct m_parent;
public int Unk00 { get { return _unk00; } }
public List<FieldBlock> Fields { get { return _fields; } }
public Struct02ea M_Root { get { return m_root; } }
public KaitaiStruct M_Parent { get { return m_parent; } }
}
}
Affiliate disclaimer: I'm a Kaitai Struct maintainer (see my GitHub profile).
Since I am wrapping each field in a field_block, the generated code stores these values in that type of object. This is incredibly inefficient when half of the generated field_block objects store a single integer. It would also require the consuming code to iterate through a list of each field block in order to get the actual field's value.
I think that rather than trying to describe the entire format with an ultimate Kaitai Struct specification, it's better for you not to let the generated code parse all the fields automatically. Move the parsing control to your application code, where you use the type Struct02ea.FieldBlock that represents the individual field and basically replicate the "repeat until end of stream" loop that the generated code that you posted was doing:
_fields = new List<FieldBlock>();
{
var i = 0;
while (!m_io.IsEof) {
_fields.Add(new FieldBlock(m_io, this, m_root));
i++;
}
}
The advantage of doing so is that you can adjust the loop to fit your needs. To avoid the overhead you describe, you'll probably want to keep the Struct02ea.FieldBlock object in a local variable inside the loop body, pull only the values you care about (save them in your compact, consumer-friendly output structures) and let it leave the scope after the loop iteration ends. This will allow each original FieldBlock object to get garbage-collected once you process it, so the overhead they have will be limited to a single instance and not multiplied by the number of fields in the file.
The most straightforward and seamless way to prevent the Kaitai Struct-generated code parse fields (but otherwise keep everything the same) is to add if: false in the KSY specification, as #webbnh suggested in a GitHub issue:
seq:
- id: unk_00
type: s4
- id: fields
type: field_block
repeat: eos
if: false # add this
The if: false works better than omitting it from seq entirely, because the kaitai-struct-compiler has occasional troubles with unused types (when compiling the KSY spec with unused types, you may get an error "Unable to derive _parent type in ..." due to a compiler bug). But with this if: false trick, you can't run into them because the field_block type is no longer unused.
I have collection with thousands of documents, in document there's field named Rate, problem is currently its type is string, so when it's not available, the old developer set it to "N/A". For now I want to change the type of this field to numeric in C# (set it to 0 when n/a), but if I do so I can't load the past data.
Can we customize the deserialization so it will convert N/A to 0?
You need to create an IBsonSerializer or SerializerBase<> and attach it to the property you wish to serialize using the BsonSerializerAttribute. Something like the following:
public class BsonStringNumericSerializer : SerializerBase<double>
{
public override double Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
{
var type = context.Reader.GetCurrentBsonType();
if (type == BsonType.String)
{
var s = context.Reader.ReadString();
if (s.Equals("N/A", StringComparison.InvariantCultureIgnoreCase))
{
return 0.0;
}
else
{
return double.Parse(s);
}
}
else if (type == BsonType.Double)
{
return context.Reader.ReadDouble();
}
// Add any other types you need to handle
else
{
return 0.0;
}
}
}
public class YourClass
{
[BsonSerializer(typeof(BsonStringNumericSerializer))]
public double YourDouble { get; set; }
}
If you don't want to use attributes you can create an IBsonSerializationProvider and register it using BsonSerializer.RegisterSerializationProvider.
Full documentation of MongoDB C# Bson serialization can be found here
the SDK 7.x is not working on Unity 5.1.0f3 , i always got the error version not found .
does someone have see this error ?
Actually, it's just a warning. But you can fix it.
There are several places where facebook plugin calls
FBBuildVersionAttribute.GetVersionAttributeOfType(typeof(AbstractFacebook));
So first, you need to modify FBBuildVersionAttribute to this:
// we are going to apply this attribute to Class
// instead of Assembly
// also make it inheritable for all implementations
[AttributeUsage(AttributeTargets.Class, Inherited = true)]
public class FBBuildVersionAttribute : Attribute
{
private DateTime buildDate;
private string buildHash;
private string buildVersion;
private string sdkVersion;
public DateTime Date { get { return buildDate; } }
public string Hash { get { return buildHash; } }
public string SdkVersion { get { return sdkVersion; } }
public string BuildVersion { get { return buildVersion; } }
public FBBuildVersionAttribute(string sdkVersion, string buildVersion)
{
this.buildVersion = buildVersion;
var parts = buildVersion.Split('.');
buildDate = DateTime.ParseExact(parts[0], "yyMMdd", System.Globalization.CultureInfo.InvariantCulture);
buildHash = parts[1];
this.sdkVersion = sdkVersion;
}
public override string ToString()
{
return buildVersion;
}
public static FBBuildVersionAttribute GetVersionAttributeOfType(Type type)
{
foreach (FBBuildVersionAttribute attribute in getAttributes(type))
{
return attribute;
}
return null;
}
private static FBBuildVersionAttribute[] getAttributes(Type type)
{
if (type == null)
throw new ArgumentNullException("type");
// we want to get attributes from type instead of assmebly
return (FBBuildVersionAttribute[])(type.GetCustomAttributes(typeof(FBBuildVersionAttribute), false));
}
}
No you just need to add this attribute to AbstractFacebook:
[FBBuildVersionAttribute("7.0.1", "150604.98558e55096475c")]
public abstract class AbstractFacebook : MonoBehaviour
{
// ...
}
Note that 98558e55096475c part is trash string. It's not actual build hash, cause I don't have one.
Get the latest version of the FB Unity SDK. Change log says it's fixed now.
https://developers.facebook.com/docs/unity/change-log
This should be easy but it's managed to confound me a few times. I'm trying to set a Value within a class using Reflection.
public class EngineeringValueClass<T> {
public T Value { get { } set { } }
}
Then in a calling class I have:
public class MyClass {
EngineeringValueClass<double> Value1;
EngineeringValueClass<double> Value2;
// Along with many others.
public void SetValueByName(object FieldName,object FieldValue) {
// Get the "Value" field of a generic EngineeringValueClass<double>
PropertyInfo MyValuePropRef =
typeof(EngineeringValueClass<double>).GetProperty("Value");
// Get the field within this class I want to set.
FieldInfo MyNameFieldRef = typeof(MyClass).GetField(FieldName.ToString());
MyValuePropRef.SetValue(MyNameFieldRef.GetValue,
FieldValue,
null);
}
}
My goal is to have
SetValueByName("Value1",2.3);
set Value1's "Value" using the set accessor. I presume my problem is that MyNameFieldRef.GetValue doesn't return an object reference but rather a "Value", but I'm not sure how to work around that. I don't want to pass "this" because that's not right either.
Okay, I finally figured this out:
public void SetValueByName(object FieldName, object FieldValue) {
Type t = typeof(MyClass);
FieldInfo PrimaryField = t.GetField(FieldName.ToString());
object ValueField = PrimaryField.GetValue(this);
// To get the type of Value
MethodInfo TypeValueField = ValueField.GetType().GetMethod("GetValueType");
Type ValueType = (Type) TypeValueField.Invoke(ValueField, null);
// I added a "GetValueType () { return typeof(T); } to EngineeringValueClass
if (ValueType == typeof(Int16))
{
((EngineeringValueClass<Int16>)ValueField).Value = Int16.Parse(FieldValue.ToString());
}...
}
The code looks like this:
StringBuilder builder = new StringBuilder();
XmlWriterSettings settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;
using (XmlWriter xmlWriter = XmlWriter.Create(builder, settings))
{
XmlSerializer s = new XmlSerializer(objectToSerialize.GetType());
s.Serialize(xmlWriter, objectToSerialize);
}
The resulting serialized document includes namespaces, like so:
<message xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"
xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\"
xmlns="urn:something">
...
</message>
To remove the xsi and xsd namespaces, I can follow the answer from How to serialize an object to XML without getting xmlns=”…”?.
I want my message tag as <message> (without any namespace attributes). How can I do this?
...
XmlSerializer s = new XmlSerializer(objectToSerialize.GetType());
XmlSerializerNamespaces ns = new XmlSerializerNamespaces();
ns.Add("","");
s.Serialize(xmlWriter, objectToSerialize, ns);
This is the 2nd of two answers.
If you want to just strip all namespaces arbitrarily from a document during serialization, you can do this by implementing your own XmlWriter.
The easiest way is to derive from XmlTextWriter and override the StartElement method that emits namespaces. The StartElement method is invoked by the XmlSerializer when emitting any elements, including the root. By overriding the namespace for each element, and replacing it with the empty string, you've stripped the namespaces from the output.
public class NoNamespaceXmlWriter : XmlTextWriter
{
//Provide as many contructors as you need
public NoNamespaceXmlWriter(System.IO.TextWriter output)
: base(output) { Formatting= System.Xml.Formatting.Indented;}
public override void WriteStartDocument () { }
public override void WriteStartElement(string prefix, string localName, string ns)
{
base.WriteStartElement("", localName, "");
}
}
Suppose this is the type:
// explicitly specify a namespace for this type,
// to be used during XML serialization.
[XmlRoot(Namespace="urn:Abracadabra")]
public class MyTypeWithNamespaces
{
// private fields backing the properties
private int _Epoch;
private string _Label;
// explicitly define a distinct namespace for this element
[XmlElement(Namespace="urn:Whoohoo")]
public string Label
{
set { _Label= value; }
get { return _Label; }
}
// this property will be implicitly serialized to XML using the
// member name for the element name, and inheriting the namespace from
// the type.
public int Epoch
{
set { _Epoch= value; }
get { return _Epoch; }
}
}
Here's how you would use such a thing during serialization:
var o2= new MyTypeWithNamespaces { ..intializers.. };
var builder = new System.Text.StringBuilder();
using ( XmlWriter writer = new NoNamespaceXmlWriter(new System.IO.StringWriter(builder)))
{
s2.Serialize(writer, o2, ns2);
}
Console.WriteLine("{0}",builder.ToString());
The XmlTextWriter is sort of broken, though. According to the reference doc, when it writes it does not check for the following:
Invalid characters in attribute and element names.
Unicode characters that do not fit the specified encoding. If the Unicode
characters do not fit the specified
encoding, the XmlTextWriter does not
escape the Unicode characters into
character entities.
Duplicate attributes.
Characters in the DOCTYPE public
identifier or system identifier.
These problems with XmlTextWriter have been around since v1.1 of the .NET Framework, and they will remain, for backward compatibility. If you have no concerns about those problems, then by all means use the XmlTextWriter. But most people would like a bit more reliability.
To get that, while still suppressing namespaces during serialization, instead of deriving from XmlTextWriter, define a concrete implementation of the abstract XmlWriter and its 24 methods.
An example is here:
public class XmlWriterWrapper : XmlWriter
{
protected XmlWriter writer;
public XmlWriterWrapper(XmlWriter baseWriter)
{
this.Writer = baseWriter;
}
public override void Close()
{
this.writer.Close();
}
protected override void Dispose(bool disposing)
{
((IDisposable) this.writer).Dispose();
}
public override void Flush()
{
this.writer.Flush();
}
public override string LookupPrefix(string ns)
{
return this.writer.LookupPrefix(ns);
}
public override void WriteBase64(byte[] buffer, int index, int count)
{
this.writer.WriteBase64(buffer, index, count);
}
public override void WriteCData(string text)
{
this.writer.WriteCData(text);
}
public override void WriteCharEntity(char ch)
{
this.writer.WriteCharEntity(ch);
}
public override void WriteChars(char[] buffer, int index, int count)
{
this.writer.WriteChars(buffer, index, count);
}
public override void WriteComment(string text)
{
this.writer.WriteComment(text);
}
public override void WriteDocType(string name, string pubid, string sysid, string subset)
{
this.writer.WriteDocType(name, pubid, sysid, subset);
}
public override void WriteEndAttribute()
{
this.writer.WriteEndAttribute();
}
public override void WriteEndDocument()
{
this.writer.WriteEndDocument();
}
public override void WriteEndElement()
{
this.writer.WriteEndElement();
}
public override void WriteEntityRef(string name)
{
this.writer.WriteEntityRef(name);
}
public override void WriteFullEndElement()
{
this.writer.WriteFullEndElement();
}
public override void WriteProcessingInstruction(string name, string text)
{
this.writer.WriteProcessingInstruction(name, text);
}
public override void WriteRaw(string data)
{
this.writer.WriteRaw(data);
}
public override void WriteRaw(char[] buffer, int index, int count)
{
this.writer.WriteRaw(buffer, index, count);
}
public override void WriteStartAttribute(string prefix, string localName, string ns)
{
this.writer.WriteStartAttribute(prefix, localName, ns);
}
public override void WriteStartDocument()
{
this.writer.WriteStartDocument();
}
public override void WriteStartDocument(bool standalone)
{
this.writer.WriteStartDocument(standalone);
}
public override void WriteStartElement(string prefix, string localName, string ns)
{
this.writer.WriteStartElement(prefix, localName, ns);
}
public override void WriteString(string text)
{
this.writer.WriteString(text);
}
public override void WriteSurrogateCharEntity(char lowChar, char highChar)
{
this.writer.WriteSurrogateCharEntity(lowChar, highChar);
}
public override void WriteValue(bool value)
{
this.writer.WriteValue(value);
}
public override void WriteValue(DateTime value)
{
this.writer.WriteValue(value);
}
public override void WriteValue(decimal value)
{
this.writer.WriteValue(value);
}
public override void WriteValue(double value)
{
this.writer.WriteValue(value);
}
public override void WriteValue(int value)
{
this.writer.WriteValue(value);
}
public override void WriteValue(long value)
{
this.writer.WriteValue(value);
}
public override void WriteValue(object value)
{
this.writer.WriteValue(value);
}
public override void WriteValue(float value)
{
this.writer.WriteValue(value);
}
public override void WriteValue(string value)
{
this.writer.WriteValue(value);
}
public override void WriteWhitespace(string ws)
{
this.writer.WriteWhitespace(ws);
}
public override XmlWriterSettings Settings
{
get
{
return this.writer.Settings;
}
}
protected XmlWriter Writer
{
get
{
return this.writer;
}
set
{
this.writer = value;
}
}
public override System.Xml.WriteState WriteState
{
get
{
return this.writer.WriteState;
}
}
public override string XmlLang
{
get
{
return this.writer.XmlLang;
}
}
public override System.Xml.XmlSpace XmlSpace
{
get
{
return this.writer.XmlSpace;
}
}
}
Then, provide a derived class that overrides the StartElement method, as before:
public class NamespaceSupressingXmlWriter : XmlWriterWrapper
{
//Provide as many contructors as you need
public NamespaceSupressingXmlWriter(System.IO.TextWriter output)
: base(XmlWriter.Create(output)) { }
public NamespaceSupressingXmlWriter(XmlWriter output)
: base(XmlWriter.Create(output)) { }
public override void WriteStartElement(string prefix, string localName, string ns)
{
base.WriteStartElement("", localName, "");
}
}
And then use this writer like so:
var o2= new MyTypeWithNamespaces { ..intializers.. };
var builder = new System.Text.StringBuilder();
var settings = new XmlWriterSettings { OmitXmlDeclaration = true, Indent= true };
using ( XmlWriter innerWriter = XmlWriter.Create(builder, settings))
using ( XmlWriter writer = new NamespaceSupressingXmlWriter(innerWriter))
{
s2.Serialize(writer, o2, ns2);
}
Console.WriteLine("{0}",builder.ToString());
Credit for this to Oleg Tkachenko.
After reading Microsoft's documentation and several solutions online, I have discovered the solution to this problem. It works with both the built-in XmlSerializer and custom XML serialization via IXmlSerialiazble.
To wit, I'll use the same MyTypeWithNamespaces XML sample that's been used in the answers to this question so far.
[XmlRoot("MyTypeWithNamespaces", Namespace="urn:Abracadabra", IsNullable=false)]
public class MyTypeWithNamespaces
{
// As noted below, per Microsoft's documentation, if the class exposes a public
// member of type XmlSerializerNamespaces decorated with the
// XmlNamespacesDeclarationAttribute, then the XmlSerializer will utilize those
// namespaces during serialization.
public MyTypeWithNamespaces( )
{
this._namespaces = new XmlSerializerNamespaces(new XmlQualifiedName[] {
// Don't do this!! Microsoft's documentation explicitly says it's not supported.
// It doesn't throw any exceptions, but in my testing, it didn't always work.
// new XmlQualifiedName(string.Empty, string.Empty), // And don't do this:
// new XmlQualifiedName("", "")
// DO THIS:
new XmlQualifiedName(string.Empty, "urn:Abracadabra") // Default Namespace
// Add any other namespaces, with prefixes, here.
});
}
// If you have other constructors, make sure to call the default constructor.
public MyTypeWithNamespaces(string label, int epoch) : this( )
{
this._label = label;
this._epoch = epoch;
}
// An element with a declared namespace different than the namespace
// of the enclosing type.
[XmlElement(Namespace="urn:Whoohoo")]
public string Label
{
get { return this._label; }
set { this._label = value; }
}
private string _label;
// An element whose tag will be the same name as the property name.
// Also, this element will inherit the namespace of the enclosing type.
public int Epoch
{
get { return this._epoch; }
set { this._epoch = value; }
}
private int _epoch;
// Per Microsoft's documentation, you can add some public member that
// returns a XmlSerializerNamespaces object. They use a public field,
// but that's sloppy. So I'll use a private backed-field with a public
// getter property. Also, per the documentation, for this to work with
// the XmlSerializer, decorate it with the XmlNamespaceDeclarations
// attribute.
[XmlNamespaceDeclarations]
public XmlSerializerNamespaces Namespaces
{
get { return this._namespaces; }
}
private XmlSerializerNamespaces _namespaces;
}
That's all to this class. Now, some objected to having an XmlSerializerNamespaces object somewhere within their classes; but as you can see, I neatly tucked it away in the default constructor and exposed a public property to return the namespaces.
Now, when it comes time to serialize the class, you would use the following code:
MyTypeWithNamespaces myType = new MyTypeWithNamespaces("myLabel", 42);
/******
OK, I just figured I could do this to make the code shorter, so I commented out the
below and replaced it with what follows:
// You have to use this constructor in order for the root element to have the right namespaces.
// If you need to do custom serialization of inner objects, you can use a shortened constructor.
XmlSerializer xs = new XmlSerializer(typeof(MyTypeWithNamespaces), new XmlAttributeOverrides(),
new Type[]{}, new XmlRootAttribute("MyTypeWithNamespaces"), "urn:Abracadabra");
******/
XmlSerializer xs = new XmlSerializer(typeof(MyTypeWithNamespaces),
new XmlRootAttribute("MyTypeWithNamespaces") { Namespace="urn:Abracadabra" });
// I'll use a MemoryStream as my backing store.
MemoryStream ms = new MemoryStream();
// This is extra! If you want to change the settings for the XmlSerializer, you have to create
// a separate XmlWriterSettings object and use the XmlTextWriter.Create(...) factory method.
// So, in this case, I want to omit the XML declaration.
XmlWriterSettings xws = new XmlWriterSettings();
xws.OmitXmlDeclaration = true;
xws.Encoding = Encoding.UTF8; // This is probably the default
// You could use the XmlWriterSetting to set indenting and new line options, but the
// XmlTextWriter class has a much easier method to accomplish that.
// The factory method returns a XmlWriter, not a XmlTextWriter, so cast it.
XmlTextWriter xtw = (XmlTextWriter)XmlTextWriter.Create(ms, xws);
// Then we can set our indenting options (this is, of course, optional).
xtw.Formatting = Formatting.Indented;
// Now serialize our object.
xs.Serialize(xtw, myType, myType.Namespaces);
Once you have done this, you should get the following output:
<MyTypeWithNamespaces>
<Label xmlns="urn:Whoohoo">myLabel</Label>
<Epoch>42</Epoch>
</MyTypeWithNamespaces>
I have successfully used this method in a recent project with a deep hierachy of classes that are serialized to XML for web service calls. Microsoft's documentation is not very clear about what to do with the publicly accesible XmlSerializerNamespaces member once you've created it, and so many think it's useless. But by following their documentation and using it in the manner shown above, you can customize how the XmlSerializer generates XML for your classes without resorting to unsupported behavior or "rolling your own" serialization by implementing IXmlSerializable.
It is my hope that this answer will put to rest, once and for all, how to get rid of the standard xsi and xsd namespaces generated by the XmlSerializer.
UPDATE: I just want to make sure I answered the OP's question about removing all namespaces. My code above will work for this; let me show you how. Now, in the example above, you really can't get rid of all namespaces (because there are two namespaces in use). Somewhere in your XML document, you're going to need to have something like xmlns="urn:Abracadabra" xmlns:w="urn:Whoohoo. If the class in the example is part of a larger document, then somewhere above a namespace must be declared for either one of (or both) Abracadbra and Whoohoo. If not, then the element in one or both of the namespaces must be decorated with a prefix of some sort (you can't have two default namespaces, right?). So, for this example, Abracadabra is the defalt namespace. I could inside my MyTypeWithNamespaces class add a namespace prefix for the Whoohoo namespace like so:
public MyTypeWithNamespaces
{
this._namespaces = new XmlSerializerNamespaces(new XmlQualifiedName[] {
new XmlQualifiedName(string.Empty, "urn:Abracadabra"), // Default Namespace
new XmlQualifiedName("w", "urn:Whoohoo")
});
}
Now, in my class definition, I indicated that the <Label/> element is in the namespace "urn:Whoohoo", so I don't need to do anything further. When I now serialize the class using my above serialization code unchanged, this is the output:
<MyTypeWithNamespaces xmlns:w="urn:Whoohoo">
<w:Label>myLabel</w:Label>
<Epoch>42</Epoch>
</MyTypeWithNamespaces>
Because <Label> is in a different namespace from the rest of the document, it must, in someway, be "decorated" with a namespace. Notice that there are still no xsi and xsd namespaces.
XmlSerializer sr = new XmlSerializer(objectToSerialize.GetType());
TextWriter xmlWriter = new StreamWriter(filename);
XmlSerializerNamespaces namespaces = new XmlSerializerNamespaces();
namespaces.Add(string.Empty, string.Empty);
sr.Serialize(xmlWriter, objectToSerialize, namespaces);
This is the first of my two answers to the question.
If you want fine control over the namespaces - for example if you want to omit some of them but not others, or if you want to replace one namespace with another, you can do this using XmlAttributeOverrides.
Suppose you have this type definition:
// explicitly specify a namespace for this type,
// to be used during XML serialization.
[XmlRoot(Namespace="urn:Abracadabra")]
public class MyTypeWithNamespaces
{
// private fields backing the properties
private int _Epoch;
private string _Label;
// explicitly define a distinct namespace for this element
[XmlElement(Namespace="urn:Whoohoo")]
public string Label
{
set { _Label= value; }
get { return _Label; }
}
// this property will be implicitly serialized to XML using the
// member name for the element name, and inheriting the namespace from
// the type.
public int Epoch
{
set { _Epoch= value; }
get { return _Epoch; }
}
}
And this serialization pseudo-code:
var o2= new MyTypeWithNamespaces() { ..initializers...};
ns.Add( "", "urn:Abracadabra" );
XmlSerializer s2 = new XmlSerializer(typeof(MyTypeWithNamespaces));
s2.Serialize(System.Console.Out, o2, ns);
You would get something like this XML:
<MyTypeWithNamespaces xmlns="urn:Abracadabra">
<Label xmlns="urn:Whoohoo">Cimsswybclaeqjh</Label>
<Epoch>97</Epoch>
</MyTypeWithNamespaces>
Notice that there is a default namespace on the root element, and there is also a distinct namespace on the "Label" element. These namespaces were dictated by the attributes decorating the type, in the code above.
The Xml Serialization framework in .NET includes the possibility to explicitly override the attributes that decorate the actual code. You do this with the XmlAttributesOverrides class and friends. Suppose I have the same type, and I serialize it this way:
// instantiate the container for all attribute overrides
XmlAttributeOverrides xOver = new XmlAttributeOverrides();
// define a set of XML attributes to apply to the root element
XmlAttributes xAttrs1 = new XmlAttributes();
// define an XmlRoot element (as if [XmlRoot] had decorated the type)
// The namespace in the attribute override is the empty string.
XmlRootAttribute xRoot = new XmlRootAttribute() { Namespace = ""};
// add that XmlRoot element to the container of attributes
xAttrs1.XmlRoot= xRoot;
// add that bunch of attributes to the container holding all overrides
xOver.Add(typeof(MyTypeWithNamespaces), xAttrs1);
// create another set of XML Attributes
XmlAttributes xAttrs2 = new XmlAttributes();
// define an XmlElement attribute, for a type of "String", with no namespace
var xElt = new XmlElementAttribute(typeof(String)) { Namespace = ""};
// add that XmlElement attribute to the 2nd bunch of attributes
xAttrs2.XmlElements.Add(xElt);
// add that bunch of attributes to the container for the type, and
// specifically apply that bunch to the "Label" property on the type.
xOver.Add(typeof(MyTypeWithNamespaces), "Label", xAttrs2);
// instantiate a serializer with the overrides
XmlSerializer s3 = new XmlSerializer(typeof(MyTypeWithNamespaces), xOver);
// serialize
s3.Serialize(System.Console.Out, o2, ns2);
The result looks like this;
<MyTypeWithNamespaces>
<Label>Cimsswybclaeqjh</Label>
<Epoch>97</Epoch>
</MyTypeWithNamespaces>
You have stripped the namespaces.
A logical question is, can you strip all namespaces from arbitrary types during serialization, without going through the explicit overrides? The answer is YES, and how to do it is in my next response.