XmlSerializer Producing XML With No Namespace Prefix

Question

I have to create an XML file with all the elements prefixed, like this:

<ps:Request num="123" xmlns:ps="www.ladieda.com">
   <ps:ClientId>5566</ps:ClientId>
<ps:Request>

When i serialize my object, c# is smart and does this:

<Request num="123" xmlns="www.ladieda.com">
   <ClientId>5566</ClientId>
<Request>

That is good, because the ps: is not necessary.

But is there a way to force C# to serialize all the prefixes?

My serialize code is this (for incoming object pObject):

String XmlizedString = null;
MemoryStream memoryStream = new MemoryStream();
XmlSerializer xs = new XmlSerializer(pObject.GetType());
XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream, Encoding.UTF8);

xs.Serialize(xmlTextWriter, pObject);
memoryStream = (MemoryStream)xmlTextWriter.BaseStream;
XmlizedString = UTF8ByteArrayToString(memoryStream.ToArray());
return XmlizedString;


private String UTF8ByteArrayToString(Byte[] characters)
{
    UTF8Encoding encoding = new UTF8Encoding();
    String constructedString = encoding.GetString(characters);
    return (constructedString);
}

Answer 1

First of all, if the consumer of your string were processing XML, then they wouldn't care about the prefix, since it doesn't matter (to XML). Perhaps they don't understand XML, and think they're processing a string (which might need to have the string "ps:" on every element).

Second of all, you should change your code a bit:

XmlSerializer xs = new XmlSerializer(pObject.GetType());
using (MemoryStream memoryStream = new MemoryStream())
{
    XmlWriterSettings settings = new XmlWriterSettings()
    {
        Encoding = Encoding.UTF8
    };
    using (XmlWriter writer = XmlWriter.Create(memoryStream, settings))
    {
        xs.Serialize(writer, pObject);
    }
    return Encoding.UTF8.GetString(memoryStream.ToArray());
}

This will properly dispose of the stream and XmlWriter if an exception is thrown, stops using the deprecated XmlTextWriter class, and yet still returns a string containing XML written for UTF-8.

Finally, to control the prefix, see "How to: Qualify XML Element and XML Attribute Names" :

XmlSerializerNamespaces myNamespaces = new XmlSerializerNamespaces();
myNamespaces.Add("ps", "www.ladieda.com");

XmlSerializer xs = new XmlSerializer(pObject.GetType());
using (MemoryStream memoryStream = new MemoryStream())
{
    XmlWriterSettings settings = new XmlWriterSettings()
    {
        Encoding = Encoding.UTF8
    };
    using (XmlWriter writer = XmlWriter.Create(memoryStream, settings))
    {
        xs.Serialize(writer, pObject, myNamespaces);
    }
    return Encoding.UTF8.GetString(memoryStream.ToArray());
}

Answer 2

Also check out XmlNamespaceDeclarationsAttribute. Caveat: when deserializing it will only give you namespaces defined by that element, it won't have namespaces defined in parent elements. If you don't have a consistent root type then use the XmlSerializer.Serialize() overload from @John Saunders.

http://msdn.microsoft.com/en-us/library/system.xml.serialization.xmlnamespacedeclarationsattribute.aspx

In another question @John Saunders suggests using this attribute in regards to controlling xmlns in WSDL: Namespace Prefixes in Wsdl (.net)

From MSDN Sample:

// C#
using System;
using System.IO;
using System.Xml.Serialization;
[XmlRoot("select")]
public class Select {
    [XmlAttribute] public string xpath;
    [XmlNamespaceDeclarations] public XmlSerializerNamespaces xmlns;
}
public class Test {
    public static void Main(string[] args) {
       Select mySelect = new Select();
       mySelect.xpath = "myNS:ref/@common:y";
       mySelect.xmlns = new XmlSerializerNamespaces();
       mySelect.xmlns.Add("MyNS", "myNS.tempuri.org");
       mySelect.xmlns.Add("common", "common.tempuri.org");
       XmlSerializer ser = new XmlSerializer(typeof(Select));
       ser.Serialize(Console.Out, mySelect);
    }
}
// Output:
// <?xml version="1.0" encoding="IBM437"?>
// <select xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmln:xsi="http://www.w3.org/2001/XMLSchema-instance" 
// xmlns:common="common.tempuri.org" xmlns:MyNS="myNS.tempuri.org" xpath="myNS:ref/@common:y" />