Xml Serialization in C#

In a number of recent projects we have had to expose web services to third parties. This requires discipline in agreeing and sticking to a XML schema for your communication.

BaseSerializableObject
To make sure our classes keep in step with our schemas we utilise a base serializable object class which provides methods for converting our objects to and from XML. Each object then implements a FromXml method that validates the XML against the appropriate schema before deserialization.

    public XmlDocument ToXml()
    {
        StringBuilder sb = new StringBuilder();
        XmlWriterSettings settings = new XmlWriterSettings();
        settings.Indent = true;
        XmlWriter writer = XmlWriter.Create(sb, settings);
        XmlSerializer serializer = new XmlSerializer(this.GetType());
        serializer.Serialize(writer, this);
        XmlDocument output = new XmlDocument();
        output.LoadXml(sb.ToString());
        return output;
    }

    protected static SerializableObject FromXml(Type type, XmlDocument input, XmlSchema schema)
    {
        byte[] data = Encoding.Unicode.GetBytes(input.OuterXml);
        using (MemoryStream ms = new MemoryStream(data))
        {
            XmlReaderSettings settings = new XmlReaderSettings();
            settings.ValidationType = ValidationType.Schema;
            settings.ValidationFlags = XmlSchemaValidationFlags.ReportValidationWarnings;
            settings.Schemas.Add(schema);
            XmlReader reader = XmlReader.Create(ms, settings);
            XmlDocument validatingDoc = new XmlDocument();
            // This will throw an error if the xml does not validate against the schema
            validatingDoc.Load(reader);
            // If we got this far then deserialize
            ms.Position = 0;
            XmlSerializer serializer = new XmlSerializer(type);
            return (SerializableObject)serializer.Deserialize(ms);
        }
    }

Attributes
To enable you to dictate the way in which your objects are serialized you can specify XML attributes above your class declaration and properties.

• Serializable
  This attribute is essential for your class to be serializable and must appear above your class declaration.
• XmlRoot
  This attribute allows you to specify information about the root element of the XML document that will be the output of your serialization.
• XmlAttribute
  This attribute allows you to specify the way in which a property of your object is serialized as an XML element.
• XmlElement
  This attribute allows you to specify the way in which a property of your object is serialized as an XML element.
• XmlIgnore
  This attribute tells the serializer not to include the property in the serialization.
• XmlArray, XmlArrayItem
  These attributes tells the serializer how to name array elements.

Example

The following is a rather contrived example to demonstrate these concepts:

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Text;
using System.Xml;
using System.Xml.Schema;
using System.Xml.Serialization;

namespace XmlSerialization
{
    [Serializable, XmlRoot(ElementName = "objectXml")]
    public class MySerializableObject : SerializableObject
    {
         private int _integerOne;
         private int _integerTwo;
         private int _integerThree;
         private int _integerFour;
         private string _stringOne;
         private string _stringTwo;
         private string _stringThree;
         private string _stringFour;
         private MySerializableObject[] _children;
 
         public MySerializableObject()
         {
         }

         public MySerializableObject(int integerOne,
                                    int integerTwo,
                                    int integerThree,
                                    int integerFour,
                                    string stringOne,
                                    string stringTwo,
                                    string stringThree,
                                    string stringFour)
         {
                  _integerOne = integerOne;
                  _integerTwo = integerTwo;
                  _integerThree = integerThree;
                  _integerFour = integerFour;
                  _stringOne = stringOne;
                  _stringTwo = stringTwo;
                  _stringThree = stringThree;
                  _stringFour = stringFour;
         }

         public static MySerializableObject FromXml(XmlDocument objectXml)
         {
                  // Load embedded Xml schema from assembly
                  XmlSchema schema = XmlSchema.Read(Assembly.GetAssembly(typeof(MySerializableObject)).GetManifestResourceStream("XmlSerialization.schemas.MySerializableObject.xsd"), null);
                  // Deserialize object from XML provided (if XML passes validation)
                  MySerializableObject obj = (MySerializableObject)SerializableObject.FromXml(typeof(MySerializableObject), objectXml, schema);
                  return obj;
         }

         [XmlElement(ElementName = "numberTwo", Order = 4)]
         public int IntegerOne
         {
                  get
                  {
                           return _integerOne;
                  }
                  set
                  {
                           _integerOne = value;
                  }
         }

         [XmlIgnore]
         public int IntegerTwo
         {
                  get
                  {
                           return _integerTwo;
                  }
                  set
                  {
                           _integerTwo = value;
                  }
         }

         [XmlElement(ElementName = "numberOne", Order = 3)]
         public int IntegerThree
         {
                  get
                  {
                           return _integerThree;
                  }
                  set
                  {
                           _integerThree = value;
                  }
         }

         [XmlAttribute(AttributeName = "integerAttribute")]
         public int IntegerFour
         {
                  get
                  {
                           return _integerFour;
                  }
                  set
                  {
                           _integerFour = value;
                  }
         }

         [XmlElement(ElementName = "textTwo", Order = 2)]
         public string StringOne
         {
                  get
                  {
                           return _stringOne;
                  }
                  set
                  {
                           _stringOne = value;
                  }
         }

         [XmlIgnore]
         public string StringTwo
         {
                  get
                  {
                           return _stringTwo;
                  }
                  set
                  {
                           _stringTwo = value;
                  }
         }

         [XmlElement(ElementName = "textOne", Order = 1)]
         public string StringThree
         {
                  get
                  {
                           return _stringThree;
                  }
                  set
                  {
                           _stringThree = value;
                  }
         }

         [XmlAttribute(AttributeName = "stringAttribute")]
         public string StringFour
         {
                  get
                  {
                           return _stringFour;
                  }
                  set
                  {
                           _stringFour = value;
                  }
         }

         [XmlArray(ElementName = "kids", Order = 5)]
         [XmlArrayItem(ElementName = "kid")]
         public MySerializableObject[] Children
         {
                  get
                  {
                           return _children;
                  }
                  set
                  {
                           _children = value;
                  }
         }
    }
}