c# - 为什么我会收到异常 "Consider using a DataContractResolver or add any types not known statically to the list of known types"

Question

我正在尝试使用 DataContractSerializer 将对象序列化为 Xml。我有以下类(class)；

[ActiveRecord(Lazy = true)]
[KnownType(typeof(RoomType))]
[DataContract]
public class Room : ActiveRecordBase<Room>
{
    [PrimaryKey]
    [DataMember]
    public virtual Int64 RoomId { get; protected set; }

    [BelongsTo("RoomTypeId")]
    [DataMember]
    public virtual RoomType RoomType { get; set; }

    [Property]
    [DataMember]
    public virtual Int64 HotelId { get; set; }

    [Property]
    [DataMember]
    public virtual string Name { get; set; }

    [Property]
    [DataMember]
    public virtual string Description { get; set; }

    public static Room[] FindByHotelId(Int64 HotelId)
    {
        return (Room[])FindAllByProperty(typeof(Room), "HotelId", HotelId);
    }
}

RoomType 类是

[ActiveRecord(Lazy = true)]
[DataContract]
public class RoomType : ActiveRecordBase<RoomType>
{
    [PrimaryKey]
    [DataMember]
    public virtual int RoomTypeId { get; protected set; }

    [Property]
    [DataMember]
    public virtual string Name { get; set; }

}

我使用下面的方法来序列化对象

    internal static XElement ObjectToXElement<T>(T source)
    {
        XDocument oXDocument = new XDocument();

        try
        {
            using (var writer = oXDocument.CreateWriter())
            {
                // write xml into the writer
                var serializer = new DataContractSerializer(source.GetType());
                serializer.WriteObject(writer, source);
            }
        }
        catch(Exception e)
        {
            using (var writer = oXDocument.CreateWriter())
            {
                // write xml into the writer
                var serializer = new DataContractSerializer(oError.GetType());
                serializer.WriteObject(writer, oError);
            }
        }

        return oXDocument.Root;
    }

我正在序列化的实际对象是；

[KnownType(typeof(List<Room>))]
[KnownType(typeof(RoomType))]
[DataContract]
public class RoomTypeResponse
{
    [DataMember]
    public int Code { get; set; }

    [DataMember]
    public string Message { get; set; }

    [DataMember]
    public List<Room> Rooms { get; set; }

    public RoomTypeResponse()
    {
        this.Rooms = new List<Room>();
    }
}

但由于某种原因，当我调用方法来序列化对象时，出现以下异常；

Type 'Castle.Proxies.RoomTypeProxy' with data contract name 'RoomTypeProxy:http://schemas.datacontract.org/2004/07/Castle.Proxies' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.

如果我注释掉 Room 类中的属性，它工作正常

[BelongsTo("RoomTypeId")]
[DataMember]
public virtual RoomType RoomType { get; set; }

我不确定为什么会出现异常，因为我已经为 RoomType 添加了 knowtype 属性？我错过了什么，导致了这个问题。

Answer 1

问题是在运行时生成一种类型 (CaSTLe.Proxies.RoomTypeProxy)，因此 .NET 对此一无所知。这不是特定于 NHibernate 的问题。如果禁用延迟加载和代理生成，问题就会消失，但我知道这可能很困难。其他选择是使用其他序列化程序，例如 BinaryFormatter，但我不知道这是否适合您。