How to serialize property of type Object with XmlSerializer

Question

I have a property:

public object Tag

but it can contain finite number of types, unfortunately without base type (except object type). But w

Answer 1

I did it implementing the IXmlSerializable interface, writing the object type as an element attribute.

  public void ReadXml(XmlReader reader)
  {
     reader.MoveToContent();

     Boolean isEmptyElement = reader.IsEmptyElement; 
     reader.ReadStartElement();
     if (!isEmptyElement)
     {

        // ...here comes all other properties deserialization

        object tag;
        if (ReadXmlObjectProperty(reader, "Tag", out tag))
        {
           Tag = tag;
        }
        reader.ReadEndElement();
     }
  }

  public void WriteXml(XmlWriter writer)
  {

     // ...here comes all other properties serialization

     WriteXmlObjectProperty(writer, "Tag", Tag);
  }

  public static bool ReadXmlObjectProperty(XmlReader reader, 
                                           string name,
                                           out object value)
  {
     value = null;

     // Moves to the element
     while (!reader.IsStartElement(name))
     {
        return false;
     }
     // Get the serialized type
     string typeName = reader.GetAttribute("Type");

     Boolean isEmptyElement = reader.IsEmptyElement; 
     reader.ReadStartElement();
     if (!isEmptyElement)
     {
        Type type = Type.GetType(typeName);

        if (type != null)
        {
           // Deserialize it
           XmlSerializer serializer = new XmlSerializer(type);
           value = serializer.Deserialize(reader);
        }
        else
        {
           // Type not found within this namespace: get the raw string!
           string xmlTypeName = typeName.Substring(typeName.LastIndexOf('.')+1);
           value = reader.ReadElementString(xmlTypeName);
        }
        reader.ReadEndElement();
     }

     return true;
  }
  public static void WriteXmlObjectProperty(XmlWriter writer, 
                                            string name,
                                            object value)
  {
     if (value != null)
     {
        Type valueType = value.GetType();
        writer.WriteStartElement(name);
        writer.WriteAttributeString("Type", valueType.FullName);
        writer.WriteRaw(ToXmlString(value, valueType));
        writer.WriteFullEndElement();
     }
  }

  public static string ToXmlString(object item, Type type) 
  {
     XmlWriterSettings settings = new XmlWriterSettings();
     settings.Encoding = Encoding.ASCII;
     settings.Indent = true;
     settings.OmitXmlDeclaration = true;
     settings.NamespaceHandling = NamespaceHandling.OmitDuplicates;

     using(StringWriter textWriter = new StringWriter()) 
     using(XmlWriter xmlWriter = XmlWriter.Create(textWriter, settings)) 
     {
        XmlSerializer serializer = new XmlSerializer(type);
        serializer.Serialize(xmlWriter, item, new XmlSerializerNamespaces(new[] { XmlQualifiedName.Empty }));
        return textWriter.ToString();
     }
  }

Note: in the code I use no namespace and ASCII encoding, those are non mandatory choices.

HTH, Cabbi