Can I make XmlSerializer ignore the namespace on deserialization?

Can I make XmlSerializer ignore the namespace (xmlns attribute) on deserialization so that it doesn't matter if the attribute is added or not or even if the attribute is bogus? I know that the source will always be trusted so I don't care about the xmlns attribute.

Yes, you can tell the XmlSerializer to ignore namespaces during de-serialization.

Define an XmlTextReader that ignores namespaces. Like so:

// helper class to ignore namespaces when de-serializing
public class NamespaceIgnorantXmlTextReader : XmlTextReader
{
    public NamespaceIgnorantXmlTextReader(System.IO.TextReader reader): base(reader) { }

    public override string NamespaceURI
    {
        get { return ""; }
    }
}

// helper class to omit XML decl at start of document when serializing
public class XTWFND  : XmlTextWriter {
    public XTWFND (System.IO.TextWriter w) : base(w) { Formatting= System.Xml.Formatting.Indented;}
    public override void WriteStartDocument () { }
}

Here's an example of how you would de-serialize using that TextReader:

public class MyType1 
{
    public string Label
    {
        set {  _Label= value; } 
        get { return _Label; } 
    }

    private int _Epoch;
    public int Epoch
    {
        set {  _Epoch= value; } 
        get { return _Epoch; } 
    }        
}



    String RawXml_WithNamespaces = @"
      <MyType1 xmlns='urn:booboo-dee-doo'>
        <Label>This document has namespaces on its elements</Label>
        <Epoch xmlns='urn:aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'>0</Epoch>
      </MyType1>";


    System.IO.StringReader sr;
    sr= new System.IO.StringReader(RawXml_WithNamespaces);
    var s1 = new XmlSerializer(typeof(MyType1));
    var o1= (MyType1) s1.Deserialize(new NamespaceIgnorantXmlTextReader(sr));
    System.Console.WriteLine("\n\nDe-serialized, then serialized again:\n");
    XmlSerializerNamespaces ns = new XmlSerializerNamespaces();
    ns.Add("urn", "booboo-dee-doo");
    s1.Serialize(new XTWFND(System.Console.Out), o1, ns);
    Console.WriteLine("\n\n");

The result is like so:

    <MyType1>
      <Label>This document has namespaces on its elements</Label>
      <Epoch>0</Epoch>
    </MyType1>

If you expect no namespace, but the input has namespaces, then you can set >Namespaces = false

on your XmlTextReader.

Exdended Wolfgang Grinfeld answer (w/o exception handling):

public static Message Convert(XmlDocument doc)
{
    Message obj;
    using (TextReader textReader = new StringReader(doc.OuterXml))
    {
        using (XmlTextReader reader = new XmlTextReader(textReader))
        {
            reader.Namespaces = false;
            XmlSerializer serializer = new XmlSerializer(typeof(Message));
            obj = (Message)serializer.Deserialize(reader);
        }
    }

    return obj;
}

Solved this by using XmlSerializer Deserialize to read from xml instead from stream. This way before xml is Deserialized, using Regex to remove xsi:type from the xml. Was doing this is Portable Class Library for Cross Platform, so did not had many other options :(. After this the deserialization seems to work fine.

Following code can help,

public static TClass Deserialize<TClass>(string xml) where TClass : class, new()
{
	var tClass = new TClass();

	xml = RemoveTypeTagFromXml(xml);

	var xmlSerializer = new XmlSerializer(typeof(TClass));
	using (TextReader textReader = new StringReader(xml))
	{
		tClass = (TClass)xmlSerializer.Deserialize(textReader);
	}
	return tClass;
}

public static string RemoveTypeTagFromXml(string xml)
{
	if (!string.IsNullOrEmpty(xml) && xml.Contains("xsi:type"))
	{
		xml = Regex.Replace(xml, @"\s+xsi:type=""\w+""", "");
	}
	return xml;
}

This does not ignore the namespace but instead expects it. I was attempting to do the same thing you were, but I've since added in validation using an XSD and the namespace is now required. So here is what I used to expect a namespace. https://stackoverflow.com/a/7730989/1856992

Why try to make the XmlSerializer forget how XML works? It's a fact of XML that two elements with the same name but different namespaces are different elements.

If you want to process XML that has no namespaces, then you should pre-process it to remove the namespaces, and then pass it to the serializer.