Control XML serialization of Dictionary<K, T>

Question

I'm investigating about XML serialization, and since I use lot of dictionary, I would like to serialize them as well. I found the following solution for that (I'm quite proud of it! :) ).

[XmlInclude(typeof(Foo))]
public class XmlDictionary<TKey, TValue>
{
    /// <summary>
    /// Key/value pair.
    /// </summary>
    public struct DictionaryItem
    {
        /// <summary>
        /// Dictionary item key.
        /// </summary>
        public TKey Key;

        /// <summary>
        /// Dictionary item value.
        /// </summary>
        public TValue Value;
    }

    /// <summary>
    /// Dictionary items.
    /// </summary>
    public DictionaryItem[] Items
    {
        get {
            List<DictionaryItem> items = new List<DictionaryItem>(ItemsDictionary.Count);

            foreach (KeyValuePair<TKey, TValue> pair in ItemsDictionary) {
                DictionaryItem item;

                item.Key = pair.Key;
                item.Value = pair.Value;

                items.Add(item);
            }

            return (items.ToArray());
        }
        set {
            ItemsDictionary = new Dictionary<TKey,TValue>();

            foreach (DictionaryItem item in value)
                ItemsDictionary.Add(item.Key, item.Value);
        }
    }

    /// <summary>
    /// Indexer base on dictionary key.
    /// </summary>
    /// <param name="key"></param>
    /// <returns></returns>
    public TValue this[TKey key]
    {
        get {
            return (ItemsDictionary[key]);
        }
        set {
            Debug.Assert(value != null);
            ItemsDictionary[key] = value;
        }
    }

    /// <summary>
    /// Delegate for get key from a dictionary value.
    /// </summary>
    /// <param name="value"></param>
    /// <returns></returns>
    public delegate TKey GetItemKeyDelegate(TValue value);

    /// <summary>
    /// Add a range of values automatically determining the associated keys.
    /// </summary>
    /// <param name="values"></param>
    /// <param name="keygen"></param>
    public void AddRange(IEnumerable<TValue> values, GetItemKeyDelegate keygen)
    {
        foreach (TValue v in values)
            ItemsDictionary.Add(keygen(v), v);
    }

    /// <summary>
    /// Items dictionary.
    /// </summary>
    [XmlIgnore]
    public Dictionary<TKey, TValue> ItemsDictionary = new Dictionary<TKey,TValue>();
}

The classes deriving from this class are serialized in the following way:

<FooDictionary xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"&gt;
<Items>
  <DictionaryItemOfInt32Foo>
    <Key/>
    <Value/>
  </DictionaryItemOfInt32XmlProcess>
<Items>

This give me a good solution, but:

• How can I control the name of the element DictionaryItemOfInt32Foo
• What happens if I define a Dictionary<FooInt32, Int32> and I have the classes Foo and FooInt32?
• Is it possible to optimize the class above?

THank you very much!

Answer 1

You can set [XmlElement(ElementName = "name")] on the class. I haven't tried this though, you might have to set it somewhere else. Setting ElementName somewhere is the way to go, anyway.

Answer 2

Use DataContractSerializer for serialization and use the CollectionDataContractAttribute to control the output.

[CollectionDataContract(Name="MyDictionary", ItemName="MyDictionaryItem")]
public class XmlDictionary<TKey, TValue>
{
    ...
}