Question

I have the following class:

public class Widget {        
    public virtual int Id { get; set; }

    [Required]
    public virtual WidgetType Type { get; set; }

    public virtual string SerializedParameters {
        get {
            return new XmlSerializer(Parameters.GetType()).Serialize(Parameters);
        } set {
            Parameters = new XmlSerializer(Assembly
                     .LoadFrom(Server.MapPath(Type.ModelAssembly))
                         .GetType(Type.ModelClass)
                ).Deserialize(value);
        }
    }

    private object _parameters;
    public virtual object Parameters {
        get {
            if (_parameters == null)
                _parameters = Activator.CreateInstance(Assembly
                        .LoadFrom(Server.MapPath(Type.ModelAssembly))
                            .GetType(Type.ModelClass)
                    );
            return _parameters;
        } set { _parameters = value; }
    }
}

The Parameters property is not mapped to the database but the SerializedParameters property is. However when it tries to get the information from the database and set the SerializedParameters (which subsequently sets the Parameters) the Type property is null and therefore an exception is thrown. I guess this depends on the order in which NHibernate sets the properties for the Widget but i can’t get it to work.

I was wondering if there was a way around this. Appreciate the help. Thanks

Answer 1

moved the deserialization in the getter from the setter because as you said the type is not there yet

public class Widget
{
    public virtual int Id { get; set; }
    public virtual WidgetType Type { get; set; }

    private string _serializedParameters;
    private virtual string SerializedParameters {
        get
        {
            return new XmlSerializer(Parameters.GetType()).Serialize(Parameters);
        }
        set
        {
            _serializedParameters = value;
        }
    }
    private object _parameters;
    public virtual object Parameters
    {
        get
        {
            if (_parameters == null)
            {
                if (!string.IsNullOrEmpty(serializedParameters))
                {
                    // code to deserialize the Parameters and set to Parameters
                    _parameters = new XmlSerializer(Assembly
                             .LoadFrom(Server.MapPath(Type.ModelAssembly))
                             .GetType(Type.ModelClass)
                         ).Deserialize(value);
                }
                else
                {
                    // no existing parameters, then create new object
                    _parameters = Activator.CreateInstance(Assembly.LoadFrom(Server.MapPath("~/bin/" + widget.Type.ParametersAssembly + ".dll")).GetType(widget.Type.ParametersClass));
                }
            }
            return _parameters;
        }
        set { _parameters = value; }
    }
}