How to XML-serialize a dictionary

Question

I have been able to serialize an IEnumerable this way:

[XmlArray("TRANSACTIONS")]
[XmlArrayItem("TRANSACTION", typeof(Record))]
public IEnumerable<BudgetRecord> Records
{
    get 
    {
        foreach(Record br in _budget)
        {
            yield return br;
        }
    }
}

However, I realised that now I need a dictionary containing a collection Dictionary<string, RecordCollection> (RecordCollection implements IEnumerable).

How can I achieve that?

Answer 1

Take a look at the folloing blog post http://blogs.msdn.com/b/psheill/archive/2005/04/09/406823.aspx and this one (not in english, but the code is useful) http://huseyint.com/2007/12/xml-serializable-generic-dictionary-tipi/

Answer 2

I have used the below for some time. It originally comes from here.

namespace SerializeDictionary
{
    // System namespaces
    using System;
    using System.Collections.Generic;
    using System.Runtime.Serialization;
    using System.Xml;
    using System.Xml.Schema;
    using System.Xml.Serialization;


    /// <summary>
    /// Represents an XML serializable collection of keys and values.
    /// </summary>
    /// <typeparam name="TKey">The type of the keys in the dictionary.</typeparam>
    /// <typeparam name="TValue">The type of the values in the dictionary.</typeparam>
    [Serializable]
    [XmlRoot("dictionary")]
    public class SerializableDictionary<TKey, TValue> : Dictionary<TKey, TValue>, IXmlSerializable
    {
        /// <summary>
        /// The default XML tag name for an item.
        /// </summary>
        private const string DEFAULTITEMTAG = "item";

        /// <summary>
        /// The default XML tag name for a key.
        /// </summary>
        private const string DEFAULTKEYTAG = "key";

        /// <summary>
        /// The default XML tag name for a value.
        /// </summary>
        private const string DEFAULTVALUETAG = "value";

        /// <summary>
        /// Initializes a new instance of the
        /// <see cref="SerializableDictionary&lt;TKey, TValue&gt;"/> class.
        /// </summary>
        public SerializableDictionary()
            : base()
        {
        }

        /// <summary>
        /// Initializes a new instance of the
        /// <see cref="SerializableDictionary&lt;TKey, TValue&gt;"/> class.
        /// </summary>
        /// <param name="info">A
        ///   <see cref="T:System.Runtime.Serialization.SerializationInfo"/> object
        ///   containing the information required to serialize the
        ///   <see cref="T:System.Collections.Generic.Dictionary`2"/>.
        /// </param>
        /// <param name="context">A
        ///   <see cref="T:System.Runtime.Serialization.StreamingContext"/> structure
        ///   containing the source and destination of the serialized stream
        ///   associated with the
        ///   <see cref="T:System.Collections.Generic.Dictionary`2"/>.
        /// </param>
        protected SerializableDictionary(
           SerializationInfo info,
           StreamingContext context)
            : base(info, context)
        {
        }

        /// <summary>
        /// Gets the XML tag name for an item.
        /// </summary>
        protected virtual string ItemTagName
        {
            get
            {
                return DEFAULTITEMTAG;
            }
        }

        /// <summary>
        /// Gets the XML tag name for a key.
        /// </summary>
        protected virtual string KeyTagName
        {
            get
            {
                return DEFAULTKEYTAG;
            }
        }

        /// <summary>
        /// Gets the XML tag name for a value.
        /// </summary>
        protected virtual string ValueTagName
        {
            get
            {
                return DEFAULTVALUETAG;
            }
        }

        /// <summary>
        /// Gets the XML schema for the XML serialization.
        /// </summary>
        /// <returns>An XML schema for the serialized object.</returns>
        public XmlSchema GetSchema()
        {
            return null;
        }

        /// <summary>
        /// Deserializes the object from XML.
        /// </summary>
        /// <param name="reader">The XML representation of the object.</param>
        public void ReadXml(XmlReader reader)
        {
            XmlSerializer keySerializer = new XmlSerializer(typeof(TKey));
            XmlSerializer valueSerializer = new XmlSerializer(typeof(TValue));
            bool wasEmpty = reader.IsEmptyElement;

            reader.Read();

            if (wasEmpty)
            {
                return;
            }

            try
            {
                while (reader.NodeType != XmlNodeType.EndElement)
                {
                    reader.ReadStartElement(this.ItemTagName);
                    try
                    {
                        TKey key;
                        TValue value;

                        reader.ReadStartElement(this.KeyTagName);
                        try
                        {
                            key = (TKey)keySerializer.Deserialize(reader);
                        }
                        finally
                        {
                            reader.ReadEndElement();
                        }

                        reader.ReadStartElement(this.ValueTagName);
                        try
                        {
                            value = (TValue)valueSerializer.Deserialize(reader);
                        }
                        finally
                        {
                            reader.ReadEndElement();
                        }

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

                    reader.MoveToContent();
                }
            }
            finally
            {
                reader.ReadEndElement();
            }
        }

        /// <summary>
        /// Serializes this instance to XML.
        /// </summary>
        /// <param name="writer">The writer to serialize to.</param>
        public void WriteXml(XmlWriter writer)
        {
            XmlSerializer keySerializer = new XmlSerializer(typeof(TKey));
            XmlSerializer valueSerializer = new XmlSerializer(typeof(TValue));

            foreach (var keyValuePair in this)
            {
                writer.WriteStartElement(this.ItemTagName);
                try
                {
                    writer.WriteStartElement(this.KeyTagName);
                    try
                    {
                        keySerializer.Serialize(writer, keyValuePair.Key);
                    }
                    finally
                    {
                        writer.WriteEndElement();
                    }

                    writer.WriteStartElement(this.ValueTagName);
                    try
                    {
                        valueSerializer.Serialize(writer, keyValuePair.Value);
                    }
                    finally
                    {
                        writer.WriteEndElement();
                    }
                }
                finally
                {
                    writer.WriteEndElement();
                }
            }
        }
    }
}