使用IXmlSerializable使创建可序列化的Dictionary

默认情况下，XmlSerializer无法序列化字典，这样让使用XmlSerializer作文件缓存或存储方式或asmx服务无法使用 IDictionary。这里可以通过实现IXmlSerializable接口来定制一个可序列化的字典 SerializableDictionary<TKey, TValue>。当然任意一种自定义类或者内置类型都可以通过实现IXmlSerializable来定制它们的可序列化格式

  /// <summary>
    /// 支持XML序列化的泛型Dictionary类 
    /// </summary>
    /// <typeparam name="TKey"></typeparam>
    /// <typeparam name="TValue"></typeparam>
    [XmlRoot("dictionary")]
    public class SerializableDictionary<TKey, TValue> : Dictionary<TKey, TValue>, IXmlSerializable 
    {
        public SerializableDictionary()
            : base()
        {
        }
        public SerializableDictionary(IDictionary<TKey, TValue> dictionary)
            : base(dictionary)
        {
        }
        public SerializableDictionary(IEqualityComparer<TKey> comparer)
            : base(comparer)
        {
        }
        public SerializableDictionary(int capacity)
            : base(capacity)
        { 
        }
        public SerializableDictionary(int capacity, IEqualityComparer<TKey> comparer)
            : base(capacity, comparer)
        {
        }
        protected SerializableDictionary(SerializationInfo info, StreamingContext context)
            : base(info, context)
        {
        }

        #region IXmlSerializable Members

        public XmlSchema GetSchema()
        {
            return null;
        }

        /// <summary>
        /// 从对象的XML表示形式生成该对象
        /// </summary>
        /// <param name="reader"></param>
        public void ReadXml(System.Xml.XmlReader reader)
        {
            XmlSerializer keySerializer = new XmlSerializer(typeof (TKey));
            XmlSerializer valueSerializer = new XmlSerializer(typeof (TValue));
            if (reader.IsEmptyElement || !reader.Read())
            {
                return;
            }

            while (reader.NodeType != XmlNodeType.EndElement)
            {
                reader.ReadStartElement("item"); //cjb:2009-05-04

                reader.ReadStartElement("key");
                TKey key = (TKey) keySerializer.Deserialize(reader);
                reader.ReadEndElement();

                reader.ReadStartElement("value");
                TValue value = (TValue) valueSerializer.Deserialize(reader);
                reader.ReadEndElement();

                reader.ReadEndElement(); 

                this.Add(key, value);
                reader.MoveToContent();
            }
            reader.ReadEndElement();
        }

        /// <summary>
        /// 将对象转换为其XML表示形式
        /// </summary>
        /// <param name="writer"></param>
        public void WriteXml(System.Xml.XmlWriter writer)
        {
            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();
            }
        }

        #endregion
    }