c# - Custom Xml Serialization of Unknown Type

Question

I'm attempting to deserialize a custom class via the XmlSerializer and having a few problems, in the fact that I don't know the type that I'm going to be deserializing (it's pluggable) and I'm having difficulty determining it.

I found this post which looks similar but can't quite get it to work with my approach because I need to deserialize an interface which is XmlSerializable.

What I've currently got is of the form. Note that I expect and need to be able to handle both class A and class B to be implemented via a plugin. So if I can avoid using the IXmlSerializable (which I don't think I can) then that would be great.

The ReadXml for A is what I'm stuck on. However if there are other changes that I can make to improve the system then I'm happy to do so.

public class A : IXmlSerializable
{
   public IB MyB { get; set;}

   public void ReadXml(System.Xml.XmlReader reader)
   {
      // deserialize other member attributes

      SeekElement(reader, "MyB");
      string typeName = reader.GetAttribute("Type");

      // Somehow need to the type based on the typename. From potentially 
      //an external assembly. Is it possible to use the extra types passed 
      //into an XMlSerializer Constructor???
      Type bType = ???

      // Somehow then need to deserialize B's Members
      // Deserialize X
      // Deserialize Y
   }

   public void WriteXml(System.Xml.XmlWriter writer)
   {
      // serialize other members as attributes

      writer.WriteStartElement("MyB");
      writer.WriteAttributeString("Type", this.MyB.GetType().ToString());
      this.MyB.WriteXml(writer);
      writer.WriteEndElement();
   }

   private void SeekElement(XmlReader reader, string elementName)
   {
      ReaderToNextNode(reader);
      while (reader.Name != elementName)
      {
         ReaderToNextNode(reader);
      }
   }

   private void ReaderToNextNode(XmlReader reader)
   {
      reader.Read();
      while (reader.NodeType == XmlNodeType.Whitespace)
      {
         reader.Read();
      }
   }
}

public interface IB : IXmlSerializable
{
}

public class B : IB
{

     public void ReadXml(XmlReader reader)
     {
         this.X = Convert.ToDouble(reader.GetAttribute("x"));
         this.Y = Convert.ToDouble(reader.GetAttribute("y"));
     }

   public void WriteXml(XmlWriter writer)
   {
      writer.WriteAttributeString("x", this.X.ToString());
      writer.WriteAttributeString("y", this.Y.ToString());
   }
}

NOTE : Updated as I realised B was supposed to use interface IB. Sorry for slightly wrong question.

Answer 1

To create an instance from a string, use one of the overloads of Activator.CreateInstance. To just get a type with that name, use Type.GetType.