How to make object property appear in xml attribute

I want to add an xml attribute to my SOAP response.

Given the following code:

using System.Collections.Generic;
[assembly: System.Runtime.Serialization.ContractNamespaceAttribute("http://www.opengis.net/ows/2.0", ClrNamespace = "MyNameSpace.OWS")]
namespace MyNameSpace.OWS
{
    public class ExceptionReport
    {
        public List<OWS.Exception> Exceptions;
        public static string version = "1.0.0";
        public ExceptionReport()
        {
            Exceptions = new List<OWS.Exception>();
        }
    }
    public class Exception
    {
        public string ExceptionText;
        public string exceptionCode;
        public Exception() {}
    }
}

What do i have to add to the above code so the following response reads:

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
   <s:开发者_C百科Body>
        ...
            <ExceptionReport xmlns="http://www.opengis.net/ows/2.0" xmlns:i="http://www.w3.org/2001/XMLSchema-instance" version="1.0.0">
        ...
   </s:Body>
</s:Envelope>

Intead of this (notice no version attribute on ExceptionReport element):

<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
   <s:Body>
        ...
            <ExceptionReport xmlns="http://www.opengis.net/ows/2.0" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
        ...
   </s:Body>
</s:Envelope>