Question

I am having an issue regarding the deserialization of an XML class. I need to use a proxy for an IList because XML does not serialize/deserialize on Interfaces. I need to use this proxy because NHibernate does not accept Lists and only accepts interfaces. My issue is only when deserializing. Serialization works fine.

public class EmailCategory
    {
        [XmlAttribute("Id")]
        public virtual long Id { get; set; }
        [XmlAttribute("Name")]
        public virtual string Name { get; set; }
        protected internal virtual IList<EmailBranch> EmailBranches { get; set; }

        [XmlArray("EmailBranches")]
        [XmlArrayItem("EmailBranch", typeof(EmailBranch)]
        public List<EmailBranch> EmailBranchesProxy {
            get { return EmailBranches != null ? EmailBranches .ToList() : null; }
            set { EmailBranches = value; }
        }
    }

Answer 1

A DTO object is probably the cleanest. There’s a whole range of issues that could crop up when you try to serialize database objects. However, if you still intend to serialize the object, here’s a possible solution:

public class EmailCategory
{
[XmlAttribute(“Id”)]
public virtual long Id { get; set; }
[XmlAttribute(“Name”)]
public virtual string Name { get; set; }
protected internal virtual IList EmailBranches { get; set; }
//private List _test = new List();

//[XmlArray("EmailBranches")]
//[XmlArrayItem("EmailBranch", typeof(EmailBranch))]
//public virtual List<EmailBranch> EmailBranchesProxy {
//    get { return EmailBranches != null ? EmailBranches.ToList() : null; }
//    set { EmailBranches = value; }
//}

[XmlArray("EmailBranches")]
[XmlArrayItem("EmailBranch", typeof(EmailBranch))]
public virtual List<EmailBranch> EmailBranchesProxy
{
    get 
    {
        var proxy = EmailBranches as List<EmailBranch>;
        if (proxy == null && EmailBranches != null)
        {
            proxy = EmailBranches.ToList();
        }

        return proxy;
    }
    set { EmailBranches = value; }
}

public EmailCategory()
{
    EmailBranches = new List<EmailBranch>();
}

}

The problem you’re having is in this line: get { return EmailBranches != null ? EmailBranches .ToList() : null; }. The deserialization process uses the get method and then adds items to the collection. Since you’re returning null or a new List object, this does not represent the original EmailBranches collection, hence the serializer correctly deserializes a new EmailBranch object, but addes it to the wrong collection.

The fix, as above, is to initialize the EmailBranches collection inside the constructor (hence it won’t be null … which is probably a good idea anyway) and then type checking in the proxy property appropriately.