How to serialize and deserialize ConfigurationElement object

Hello,

I need serialize and desirelize objects of Configuration Manager (http://msdn.microsoft.com/en-us/library/system.configuration.configurationmanager.aspx).
This is part of my code:

    [Serializable]
    public class PropertyElement : ConfigurationElement
    {
        public PropertyElement() { }

        [ConfigurationProperty("name", IsKey = true)]
        public string Name
        {
            get { return ((string)(base["name"])); }
            set { base["name"] = value; }
        }

        [ConfigurationProperty("value")]
        public string Value
        {
            get { return ((string)(base["value"])); }
            set { base["value"] = value; }
        }
    }

An exception occurs when I try to serialize ConfigurationElement:

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

Exception:
An unhandled exception of type 'System.InvalidOperationException' occurred in System.Xml.dll
Additional information: There was an error reflecting type 'CustomConfigLoader.PropertyElement'.
InnerException:"You must implement a default accessor on System.Configuration.ConfigurationLockCollection because it inherits from ICollection."

How to serialize and deserialize ConfigurationElement object ?