Can I serialize Anonymous Types as xml?

Something like this should get you started...

class Program
{
    static void Main(string[] args)
    {
        var me = new
        {
            Hello = "World",
            Other = new
            {
                My = "Object",
                V = 1,
                B = (byte)2
            }
        };

        var x = me.ToXml();
    }
}
public static class Tools
{
    private static readonly Type[] WriteTypes = new[] {
        typeof(string), typeof(DateTime), typeof(Enum), 
        typeof(decimal), typeof(Guid),
    };
    public static bool IsSimpleType(this Type type)
    {
        return type.IsPrimitive || WriteTypes.Contains(type);
    }
    public static XElement ToXml(this object input)
    {
        return input.ToXml(null);
    }
    public static XElement ToXml(this object input, string element)
    {
        if (input == null)
            return null;

        if (string.IsNullOrEmpty(element))
            element = "object";
        element = XmlConvert.EncodeName(element);
        var ret = new XElement(element);

        if (input != null)
        {
            var type = input.GetType();
            var props = type.GetProperties();

            var elements = from prop in props
                           let name = XmlConvert.EncodeName(prop.Name)
                           let val = prop.GetValue(input, null)
                           let value = prop.PropertyType.IsSimpleType()
                                ? new XElement(name, val)
                                : val.ToXml(name)
                           where value != null
                           select value;

            ret.Add(elements);
        }

        return ret;
    }
}

... resulting xml ...

<object>
  <Hello>World</Hello>
  <Other>
    <My>Object</My>
    <V>1</V>
    <B>2</B>
  </Other>
</object>

It can't be accomplished using XmlSerializer nor DataContractSerializer. It can be done by a manually written code, as demonstrated below (I can't comment as to whether the code is comprehensive enough to handle all types - but it's a very good start).