How to serialize an object to XML without getting xmlns="..."?

Question

Ahh... nevermind. It's always the search after the question is posed that yields the answer. My object that is being serialized is obj and has already been defined. Adding an XMLSerializerNamespace with a single empty namespace to the collection does the trick.

In VB like this:

Dim xs As New XmlSerializer(GetType(cEmploymentDetail))
Dim ns As New XmlSerializerNamespaces()
ns.Add("", "")

Dim settings As New XmlWriterSettings()
settings.OmitXmlDeclaration = True

Using ms As New MemoryStream(), _
    sw As XmlWriter = XmlWriter.Create(ms, settings), _
    sr As New StreamReader(ms)
    xs.Serialize(sw, obj, ns)
    ms.Position = 0
    Console.WriteLine(sr.ReadToEnd())
End Using

in C# like this:

//Create our own namespaces for the output
XmlSerializerNamespaces ns = new XmlSerializerNamespaces();

//Add an empty namespace and empty value
ns.Add("", "");

//Create the serializer
XmlSerializer slz = new XmlSerializer(someType);

//Serialize the object with our own namespaces (notice the overload)
slz.Serialize(myXmlTextWriter, someObject, ns);

If you want to get rid of the extra xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" and xmlns:xsd="http://www.w3.org/2001/XMLSchema", but still keep your own namespace xmlns="http://schemas.YourCompany.com/YourSchema/", you use the same code as above except for this simple change:

//  Add lib namespace with empty prefix  
ns.Add("", "http://schemas.YourCompany.com/YourSchema/");   

If you want to remove the namespace you may also want to remove the version, to save you searching I've added that functionality so the below code will do both.

I've also wrapped it in a generic method as I'm creating very large xml files which are too large to serialize in memory so I've broken my output file down and serialize it in smaller "chunks":

    public static string XmlSerialize<T>(T entity) where T : class
    {
        // removes version
        XmlWriterSettings settings = new XmlWriterSettings();
        settings.OmitXmlDeclaration = true;

        XmlSerializer xsSubmit = new XmlSerializer(typeof(T));
        using (StringWriter sw = new StringWriter())
        using (XmlWriter writer = XmlWriter.Create(sw, settings))
        {
            // removes namespace
            var xmlns = new XmlSerializerNamespaces();
            xmlns.Add(string.Empty, string.Empty);

            xsSubmit.Serialize(writer, entity, xmlns);
            return sw.ToString(); // Your XML
        }
    }

I Suggest this helper class:

public static class Xml
{
    #region Fields

    private static readonly XmlWriterSettings WriterSettings = new XmlWriterSettings {OmitXmlDeclaration = true, Indent = true};
    private static readonly XmlSerializerNamespaces Namespaces = new XmlSerializerNamespaces(new[] {new XmlQualifiedName("", "")});

    #endregion

    #region Methods

    public static string Serialize(object obj)
    {
        if (obj == null)
        {
            return null;
        }

        return DoSerialize(obj);
    }

    private static string DoSerialize(object obj)
    {
        using (var ms = new MemoryStream())
        using (var writer = XmlWriter.Create(ms, WriterSettings))
        {
            var serializer = new XmlSerializer(obj.GetType());
            serializer.Serialize(writer, obj, Namespaces);
            return Encoding.UTF8.GetString(ms.ToArray());
        }
    }

    public static T Deserialize<T>(string data)
        where T : class
    {
        if (string.IsNullOrEmpty(data))
        {
            return null;
        }

        return DoDeserialize<T>(data);
    }

    private static T DoDeserialize<T>(string data) where T : class
    {
        using (var ms = new MemoryStream(Encoding.UTF8.GetBytes(data)))
        {
            var serializer = new XmlSerializer(typeof (T));
            return (T) serializer.Deserialize(ms);
        }
    }

    #endregion
}

:)

If you are unable to get rid of extra xmlns attributes for each element, when serializing to xml from generated classes (e.g.: when xsd.exe was used), so you have something like:

<manyElementWith xmlns="urn:names:specification:schema:xsd:one" />

then i would share with you what worked for me (a mix of previous answers and what i found here)

explicitly set all your different xmlns as follows:

Dim xmlns = New XmlSerializerNamespaces()
xmlns.Add("one", "urn:names:specification:schema:xsd:one")
xmlns.Add("two",  "urn:names:specification:schema:xsd:two")
xmlns.Add("three",  "urn:names:specification:schema:xsd:three")

then pass it to the serialize

serializer.Serialize(writer, object, xmlns);

you will have the three namespaces declared in the root element and no more needed to be generated in the other elements which will be prefixed accordingly

<root xmlns:one="urn:names:specification:schema:xsd:one" ... />
   <one:Element />
   <two:ElementFromAnotherNameSpace /> ...