In-Depth

Serialize Arrays and ArrayLists to XML

The XmlSerializer class provides a great way to convert objects to XML and back. However, it can be difficult to serialize collections such as Arrays and ArrayLists properly unless you know a few tricks.

• By Dan Wahlin
• 02/01/2004

Technology Toolbox: XML

The XmlSerializer class provides a great way to convert (serialize) objects to XML and back (deserialize). However, it can be difficult to serialize collections such as Arrays and ArrayLists properly unless you know a few tricks.

This sample application demonstrates how you can add multiple Car class instances into an Array as well as an ArrayList, then serialize them into an XML structure. You can accomplish this serialization process by using special XML serialization attributes such as XmlArray and XmlArrayItem, found in the System.Xml.Serialization namespace. For example, this code demonstrates how you can identify the type within an ArrayList using the XmlArrayItem attribute along with the C# typeof keyword:

[XmlArray("carsArrayList")]
[XmlArrayItem("car",typeof(Car))]
public ArrayList CarsCollection {
   get {
      return _CarsList;
   }
   set {
      _CarsList = value;
   }
}

Here's the output generated by serializing the ArrayList:

<?xml version="1.0" encoding="utf-16"?>
<carsCollection xmlns:xsd="http://www.w3.org/2001/XMLSchema"
   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   <carsArrayList>
      <car>
         <license>1234</license>
         <color>Black</color>
      </car>
      <car>
         <license>4321</license>
         <color>Blue</color>
      </car>
   </carsArrayList>
</carsCollection>

Download the sample here. To view a live example, visit the XML for ASP.NET Developers Web site.

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