using System;

using System.Xml.Serialization;

​

public class Program

{

    public static void Main()

    {

        var xs = new XmlSerializer(typeof(mainelement));

​

        var e = new mainelement

        {

            subelement = new subelement

            {

                otherAttr = "value"

            }

        };

​

        xs.Serialize(Console.Out, e);

    }

}

​

public class mainelement

{

    [XmlElement(Namespace = "http://example.com/xml")]

    public subelement subelement { get; set; }

}

​

public class subelement

{

    [XmlAttribute]

    public string otherAttr { get; set; }    

}