XmlSerializer.Serialize Stripping the <xml> tag

Question

I am trying to get communicate to a payment processor. When I use XmlSerializer.Serialize on my object I get

<?xml version=\"1.0\" encoding=\"utf-16\"?>
<txn xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\">
  <ssl_merchant_id>xxxxxx</ssl_merchant_id>
  <ssl_user_id>xxxxxx</ssl_user_id>
  <ssl_pin>xxxxxx</ssl_pin>
  <ssl_test_mode>True</ssl_test_mode>
  <ssl_transaction_type>ccavsonly</ssl_transaction_type>
  <ssl_card_number>4111111111111111</ssl_card_number>
  <ssl_exp_date>0612</ssl_exp_date>
  <ssl_avs_address>101 Main St.</ssl_avs_address>
  <ssl_avs_zip>90210</ssl_avs_zip>
</txn>

Prior to using that method, I manually built the XML for testing and this worked:

<txn>
  <ssl_merchant_id>xxxxxx</ssl_merchant_id>
  <ssl_user_id>xxxxxx</ssl_user_id>
  <ssl_pin>xxxxxx</ssl_pin>
  <ssl_test_mode>True</ssl_test_mode>
  <ssl_transaction_type>ccavsonly</ssl_transaction_type>
  <ssl_card_number>4111111111111111</ssl_card_number>
  <ssl_exp_date>0612</ssl_exp_date>
  <ssl_avs_address>101 Main St.</ssl_avs_address>
  <ssl_avs_zip>90210</ssl_avs_zip>
</txn>

How would I go about stripping out the <?xml version=\"1.0\" encoding=\"utf-16\"?> and xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xmlns:xsd=\"http://www.w3.org/2001/XMLSchema\"> from the XML or not have the serializer generate it to begin with?

My object looks like:

[XmlRoot(ElementName="txn")]
public class AvsTransmission
{
    [XmlElement]
    public string ssl_merchant_id { get; set; }
    [XmlElement]
    public string ssl_user_id { get; set; }
    [XmlElement]
    public string ssl_pin { get; set; }
    [XmlElement]
    public string ssl_test_mode { get; set; }
    [XmlElement]
    public string ssl_transaction_type { get; set; }
    [XmlElement]
    public string ssl_card_number { get; set; }
    [XmlElement]
    public string ssl_exp_date { get; set; }
    [XmlElement]
    public string ssl_avs_address { get; set; }
    [XmlElement]
    public string ssl_avs_zip { get; set; }
}

Answer 1

My first answer was only half of the problem, you also have to remove the declaration as has been mentioned.

Here is an example:

XmlWriterSettings settings = new XmlWriterSettings();
settings.OmitXmlDeclaration = true;

MemoryStream ms = new MemoryStream();
XmlWriter writer = XmlWriter.Create(ms, settings);

XmlSerializerNamespaces names = new XmlSerializerNamespaces();
names.Add("", "");

XmlSerializer cs = new XmlSerializer(typeof(Cat));

cs.Serialize(writer, new Cat { Lives = 9 }, names);

ms.Flush();
ms.Seek(0, SeekOrigin.Begin);
StreamReader sr = new StreamReader(ms);
var xml = sr.ReadToEnd();

The string xml now contains:

<cat><Lives>9</Lives></cat>

Answer 2

First function convert object to xml string, the second one convert object and write xml to file simultaneously.

    public static string Serialize<T>(T obj)
    {
        XmlWriterSettings settings = new XmlWriterSettings();
        settings.OmitXmlDeclaration = true;
        var writer = new StringWriter();
        XmlWriter xmlWriter = XmlWriter.Create(writer, settings);

        XmlSerializerNamespaces names = new XmlSerializerNamespaces();
        names.Add("", "");

        XmlSerializer serializer = new XmlSerializer(typeof(T));

        serializer.Serialize(xmlWriter, obj, names);
        var xml = writer.ToString();
        return xml;
    }

    public static void Serialize<T>(T obj, string filepath)
    {
        XmlWriterSettings settings = new XmlWriterSettings();
        settings.OmitXmlDeclaration = true;
        var writer = new StreamWriter(filepath);
        XmlWriter xmlWriter = XmlWriter.Create(writer, settings);

        XmlSerializerNamespaces names = new XmlSerializerNamespaces();
        names.Add("", "");

        XmlSerializer serializer = new XmlSerializer(typeof(T));

        serializer.Serialize(xmlWriter, obj, names);
    }

Actually I realized that code repeat yourself. In these methods, change only one thing which is writer object, so the code must be like below. In these way, you can easily use code just by changing writer object type.

    public static string Serialize<T>(T obj)
    {
        var writer = new StringWriter();
        Serialize<T>(obj,writer);
        var xml = writer.ToString();
        return xml;
    }

    public static void Serialize<T>(T obj, string filepath)
    {
        var writer = new StreamWriter(filepath);
        Serialize<T>(obj,writer);
    }

    public static void Serialize<T>(T obj, TextWriter writer)
    {
        XmlWriterSettings settings = new XmlWriterSettings();
        settings.OmitXmlDeclaration = true;
        XmlWriter xmlWriter = XmlWriter.Create(writer, settings);            
        XmlSerializerNamespaces names = new XmlSerializerNamespaces();
        names.Add("", "");            
        XmlSerializer serializer = new XmlSerializer(typeof(T));            
        serializer.Serialize(xmlWriter, obj, names);
    }