Comments on: Serializing an IDictionary object

By: Martin

Martin — Mon, 21 Dec 2009 13:21:19 +0000

Putting this in your class containing the hashtable works when serializing a hierarchy in which your hashtable is just one of many elemtent.

public DictionarySerializer ParametersXML
{
get { return new DictionarySerializer(parameters); }
set { parameters = (Hashtable) ((DictionarySerializer)value).Dictionary; }
}

In order for this to work you need to make the second constructor public and add a Property like so:

[XmlIgnoreAttribute]
public IDictionary Dictionary
{
get { return dictionary; }
set { dictionary = value; }
}

By: Pavel Golodoniuc

Pavel Golodoniuc — Sat, 15 Aug 2009 09:30:35 +0000

Thank you Matt for the great idea you have implemented here. It has saved me some time reinventing the wheel. I have slightly improved your DictionarySerializer class so that now it also allows to serialize contained objects as XML providing that they implement IXmlSerializable interface. I thought that it might be worth sharing it with others.

public class DictionarySerializer : IXmlSerializable
{
private IDictionary _dictionary = null;

private DictionarySerializer()
{
_dictionary = new Hashtable();
}

private DictionarySerializer(IDictionary dictionary)
{
_dictionary = dictionary;
}

public static void Serialize(IDictionary dictionary, Stream stream)
{
DictionarySerializer ds = new DictionarySerializer(dictionary);
XmlSerializer xs = new XmlSerializer(typeof(DictionarySerializer));
xs.Serialize(stream, ds);
}

public static void Serialize(IDictionary dictionary, TextWriter textWriter)
{
DictionarySerializer ds = new DictionarySerializer(dictionary);
XmlSerializer xs = new XmlSerializer(typeof(DictionarySerializer));
xs.Serialize(textWriter, ds);
}

public static void Serialize(IDictionary dictionary, XmlWriter xmlWriter)
{
DictionarySerializer ds = new DictionarySerializer(dictionary);
XmlSerializer xs = new XmlSerializer(typeof(DictionarySerializer));
xs.Serialize(xmlWriter, ds);
}

public static IDictionary Deserialize(Stream stream)
{
XmlSerializer xs = new XmlSerializer(typeof(DictionarySerializer));
DictionarySerializer ds = (DictionarySerializer)xs.Deserialize(stream);
return ds._dictionary;
}

public static IDictionary Deserialize(TextReader textReader)
{
XmlSerializer xs = new XmlSerializer(typeof(DictionarySerializer));
DictionarySerializer ds = (DictionarySerializer)xs.Deserialize(textReader);
return ds._dictionary;
}

public static IDictionary Deserialize(XmlReader xmlReader)
{
XmlSerializer xs = new XmlSerializer(typeof(DictionarySerializer));
DictionarySerializer ds = (DictionarySerializer)xs.Deserialize(xmlReader);
return ds._dictionary;
}

#region IXmlSerializable Members

XmlSchema IXmlSerializable.GetSchema()
{
return null;
}

void IXmlSerializable.ReadXml(XmlReader reader)
{
reader.Read();
reader.ReadStartElement(”dictionary”);
while (reader.NodeType != XmlNodeType.EndElement)
{
reader.ReadStartElement(”item”);
string key = reader.ReadElementString(”key”);

// Read value
string sType = reader.GetAttribute(”type”);
if (sType == null)
_dictionary.Add(key, reader.ReadElementString(”value”));
else
{
reader.ReadStartElement(”value”);
Type valuetype = Type.GetType(sType);
XmlSerializer xs = new XmlSerializer(valuetype);
_dictionary.Add(key, xs.Deserialize(reader));
reader.ReadEndElement();
reader.ReadEndElement();
}

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

void IXmlSerializable.WriteXml(XmlWriter writer)
{
writer.WriteStartElement(”dictionary”);
foreach (object key in _dictionary.Keys)
{
object value = _dictionary[key];
writer.WriteStartElement(”item”);
writer.WriteElementString(”key”, key.ToString());

// Serialize value
Type valuetype = value.GetType();
if (valuetype.GetInterface(”System.Xml.Serialization.IXmlSerializable”) == null)
writer.WriteElementString(”value”, value.ToString());
else
{
XmlSerializer xs = new XmlSerializer(valuetype);
writer.WriteStartElement(”value”);
writer.WriteAttributeString(”type”, valuetype.FullName);
xs.Serialize(writer, value);
writer.WriteEndElement();
}

writer.WriteEndElement();
}
writer.WriteEndElement();
}

#endregion
}

By: Aaron

Aaron — Tue, 16 Dec 2008 12:35:15 +0000

Thanks for providing the code Matt.

I find the IDictionary objects like HashTables and SortedLists to be incredibly useful so being able to serialise them is a must for me.

By: Tyler

Tyler — Fri, 31 Oct 2008 16:41:58 +0000

Answered my own question. I just had to set the class to public, and excuse my stupidity, but that’s never something I’ve had to do so I didn’t even know it was possible!!

By: Tyler

Tyler — Fri, 31 Oct 2008 02:17:29 +0000

I tried to implement this class, but at the line “XmlSerializer xs = new XmlSerializer(typeof(DictionarySerializer))” in the first function I call, Serialization, I get the run time error: “DictionarySerializer is inaccessible due to its protection level.” I’ve tried to set a bunch of things to public. I am calling the function from another class like: DictionarySerializer.Serialize(ht,fs), where hs and fs are a Hashtable and FileStream respectively.

Any ideas why?

By: Deployment Zone » IDictionary<TKey,TValue>, IXmlSerializable, and lambdas

Fri, 19 Sep 2008 17:29:49 +0000

[...] originally used some somewhat dated code I found on Matt Berther’s blog and while it worked, it gave me the nodey version I didn’t care much [...]

By: pepz

pepz — Sun, 22 Jun 2008 00:49:36 +0000

I think the function ‘ReadXml’ needs an extra function call to ‘reader.ReadEndElement()’ to fully close out the working node. This should allow it to work within larger object graphs as well.

By: Nikhil Shah

Nikhil Shah — Fri, 21 Mar 2008 07:26:41 +0000

This works very well,
gooood work ,
data gets serialized successfully,
but does not gets deserialize !!!
my problem is smwht like this, I have Four hashtable that stores the key n value pair,
on Form I have 4 combobox n 4 respective textbox ,
I wnt to populate the Key in combobx n Its RESPECTIVE value in textbox
on the selectedindex event of the combx, I where I write a code
I gets an error, tht there is a problem with XML document !!!
this XMl doc is well-formed, No-bugs thr..
this means tht the data is nt deserializing …

If you get this, plz help me out m stuck in this prblm since last 2 days :(

By: Simon

Simon — Wed, 10 Oct 2007 16:16:46 +0000

Hmm, that comment has mangled some of the XML tags that were in the code, the method won’t work as it is shown on this page

By: Simon

Simon — Wed, 10 Oct 2007 16:15:22 +0000

Everything being serialized as a string, and the non-recursive nature of the serialization make this kind of useless. I’ve ended up writing a couple of helper methods that will serialize and deserialize nested IDictionary objects too.

public static StringBuilder Serialize(StringBuilder sb, object obj) { if (typeof(IDictionary).IsAssignableFrom(obj.GetType())) { sb.Append(""); foreach (object key in ((IDictionary)obj).Keys) { sb.Append(""); Serialize(sb, ((IDictionary)obj)[key]); sb.Append(""); } sb.Append(""); } else { StringWriter sw = new StringWriter(sb); XmlSerializer xs = new XmlSerializer(obj.GetType()); sb.Append(""); //need a bodge in here to deal with unnamed datatables xs.Serialize(sw, obj); sb.Append(""); }


            return sb.Replace("", "");

        }
        public static object Deserialize(string s)

        {

            Object obj = new Object();
            XmlDocument xml = new XmlDocument();

            xml.LoadXml(s);
            XmlNode node = xml.ChildNodes[0];

            if (node.Name.Contains("IDictionary_"))

            {

                obj = Activator.CreateInstance(Type.GetType(XmlConvert.DecodeName(node.Name.Replace("IDictionary_", ""))));

                foreach (XmlNode child in node.ChildNodes)

                    ((IDictionary)obj).Add(child.Name.Replace("Key_", ""), Deserialize(child.InnerXml));

            }

            else if (node.Name.Contains("Type_"))

            {

                StringReader sr = new StringReader("" + node.InnerXml);

                XmlSerializer xs = new XmlSerializer(Type.GetType(XmlConvert.DecodeName(node.Name.Replace("Type_", ""))));

                obj = xs.Deserialize(sr);

            }

return obj; }

Use it like this:
Hashtable ht1 = new Hashtable(); ht1["1"] = 1; ht1["2"] = 2;


        Hashtable ht2 = new Hashtable();

        ht2["a"] = "a";

        ht2["b"] = "b";
        ht1["3"] = ht2;

Serialize(new StringBuilder(), ht1);