c# change ElementName

I have the following class:

 [Serializable]
public class UniversalRequest
{
    [XmlElement(ElementName ="TEMP")]
    public string Item { get; set; }
}

and I would like to change the ElementName of Item dynamically.

I tried the following but unsuccessfully:

foreach (PropertyInfo property in GetType().GetProperties())
{
    if (property.Name.Equals("Item"))
    {
        var attr = from a in (property.GetCustomAttributes(true))
                   where (a.GetType() == typeof(XmlElementAttribute))
                   select a;

        var xmlElementAttribute = (XmlElementAttribute)attr.SingleOrDefault();
        if (xmlElementAttribute != null)
            xmlElementAttribute.ElementName = "NEWITEMNAME";


    }
}

seems like the ElementName has been set to the new value but it back to be "TEMP" on the next iteration. thanks in advance for any assistance.