Question

I’m trying to serialize an object to XML that has a number of properties, some of which are readonly.

public Guid Id { get; private set; }

I have marked the class [Serializable] and I have implemented the ISerializable interface.

Below is the code I’m using to serialize my object.

public void SaveMyObject(MyObject obj)
{
    XmlSerializer serializer = new XmlSerializer(typeof(MyObject));
    TextWriter tw = new StreamWriter(_location);
    serializer.Serialize(tw, obj);
    tw.Close();
}

Unfortunately it falls over on the first line with this message.

InvalidOperationException was unhandled:
Unable to generate a temporary class (result=1).
error CS0200: Property or indexer ‘MyObject.Id’ cannot be assigned to — it is read only

If I set the Id property to public it works fine. Can someone tell me if I’m doing something, or at least if its even possible?

Answer 1

You could use DataContractSerializer (but note you can’t use xml attributes – only xml elements):

using System;
using System.Runtime.Serialization;
using System.Xml;
[DataContract]
class MyObject {
    public MyObject(Guid id) { this.id = id; }
    [DataMember(Name="Id")]
    private Guid id;
    public Guid Id { get {return id;}}
}
static class Program {
    static void Main() {
        var ser = new DataContractSerializer(typeof(MyObject));
        var obj = new MyObject(Guid.NewGuid());
        using(XmlWriter xw = XmlWriter.Create(Console.Out)) {
            ser.WriteObject(xw, obj);
        }
    }
}

Alternatively, you can implement IXmlSerializable and do everything yourself – but this works with XmlSerializer, at least.