XML serialization of hash table(C#3.0) - c#-3.0

Question

Hi I am trying to serialize a hash table but not happening
private void Form1_Load(object sender, EventArgs e)
{
Hashtable ht = new Hashtable();
DateTime dt = DateTime.Now;
for (int i = 0; i < 10; i++)
ht.Add(dt.AddDays(i), i);
SerializeToXmlAsFile(typeof(Hashtable), ht);
}
private void SerializeToXmlAsFile(Type targetType, Object targetObject)
{
try
{
string fileName = #"C:\output.xml";
//Serialize to XML
XmlSerializer s = new XmlSerializer(targetType);
TextWriter w = new StreamWriter(fileName);
s.Serialize(w, targetObject);
w.Flush();
w.Close();
}
catch (Exception ex) { throw ex; }
}
After a google search , I found that objects that impelment IDictonary cannot be serialized. However, I got success with binary serialization.
But I want to have xml one. Is there any way of doing so?
I am using C#3.0
Thanks

Answer 1

First of all starting with C# 2.0 you can use type safe version of very old Hashtable which come from .NET 1.0. So you can use Dictionary<DateTime, int>.
Starting with .NET 3.0 you can use DataContractSerializer. So you can rewrite you code like following
private void Form1_Load(object sender, EventArgs e)
{
MyHashtable ht = new MyHashtable();
DateTime dt = DateTime.Now;
for (int i = 0; i < 10; i++)
ht.Add(dt.AddDays(i), i);
SerializeToXmlAsFile(typeof(Hashtable), ht);
}
where SerializeToXmlAsFile and MyHashtable type you define like following:
[CollectionDataContract (Name = "AllMyHashtable", ItemName = "MyEntry",
KeyName = "MyDate", ValueName = "MyValue")]
public class MyHashtable : Dictionary<DateTime, int> { }
private void SerializeToXmlAsFile(Type targetType, Object targetObject)
{
try {
string fileName = #"C:\output.xml";
DataContractSerializer s = new DataContractSerializer (targetType);
XmlWriterSettings settings = new XmlWriterSettings ();
settings.Indent = true;
settings.IndentChars = (" ");
using (XmlWriter w = XmlWriter.Create (fileName, settings)) {
s.WriteObject (w, targetObject);
w.Flush ();
}
}
catch (Exception ex) { throw ex; }
}
This code produce C:\output.xml file with the following contain:
<?xml version="1.0" encoding="utf-8"?>
<AllMyHashtable xmlns:i="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://schemas.datacontract.org/2004/07/DataContractXmlSerializer">
<MyEntry>
<MyDate>2010-06-09T22:30:00.9474539+02:00</MyDate>
<MyValue>0</MyValue>
</MyEntry>
<MyEntry>
<MyDate>2010-06-10T22:30:00.9474539+02:00</MyDate>
<MyValue>1</MyValue>
</MyEntry>
<!-- ... -->
</AllMyHashtable>
So how we can see all names of the elements of the destination XML files we can free define.

Answer 2

You can create your own Hashtable derived from standart Hashtable with implementation of IXmlSerializable. So you will implmenent ReadXml(XmlReader reader) & WriteXml(XmlWriter writer) where you can put your own logic on how to read and write values from your Hashtablw with given XmlReader & XmlWriter.

Answer 3

I suggest you use DataContractSerializer, it's more powerful and easier to use.