Mine

 [XmlRoot("dictionary")]
    public class SerializableDictionary<TKey, TValue> : Dictionary<TKey, TValue>, IXmlSerializable {
        #region IXmlSerializable Members
        public System.Xml.Schema.XmlSchema GetSchema() {
            return null;
        }

        public void ReadXml(System.Xml.XmlReader reader) {
            XmlSerializer keySerializer = new XmlSerializer(typeof(TKey));
            XmlSerializer valueSerializer = new XmlSerializer(typeof(TValue));

            bool wasEmpty = reader.IsEmptyElement;
            reader.Read();
            if(wasEmpty)
                return;
            reader.ReadStartElement();
            while(reader.NodeType != System.Xml.XmlNodeType.None && reader.NodeType != System.Xml.XmlNodeType.EndElement) {
                reader.ReadStartElement("item");
                reader.ReadStartElement("key");
                TKey key = (TKey)keySerializer.Deserialize(reader);
                reader.ReadEndElement();
                reader.ReadStartElement("value");
                TValue value = (TValue)valueSerializer.Deserialize(reader);
                reader.ReadEndElement();
                this.Add(key, value);
                reader.ReadEndElement();
                reader.MoveToContent();
            }
            reader.ReadEndElement();
        }

        public void WriteXml(System.Xml.XmlWriter writer) {
            writer.WriteStartElement("dictionary");
            XmlSerializer keySerializer = new XmlSerializer(typeof(TKey));
            XmlSerializer valueSerializer = new XmlSerializer(typeof(TValue));

            foreach(TKey key in this.Keys) {
                writer.WriteStartElement("item");
                writer.WriteStartElement("key");
                keySerializer.Serialize(writer, key);
                writer.WriteEndElement();
                writer.WriteStartElement("value");
                TValue value = this[key];
                valueSerializer.Serialize(writer, value);
                writer.WriteEndElement();
                writer.WriteEndElement();
            }
            writer.WriteEndElement();

        }
        #endregion
    }