Cannot Serialize a List<> of DynamicProxy2-generated objects with DataContractJsonSerializer

Question

I'm running into an issue using System.Runtime.Serialization.Json.DataContractJsonSerializer to serialize a List<T> of proxied objects. It works fine with a single proxied object, but the List makes it blow up. Something like this:

using System.Collections.Generic;
using System.Runtime.Serialization;
using Castle.DynamicProxy;
using System.IO;
using NUnit.Framework;

[DataContract] 
public class SimpleViewModel 
{ 
    [DataMember] 
    public virtual int ID { get; set; } 
} 
[Test] 
public void TestSerializeArray() 
{ 
    // Generates a proxy of type "SimpleViewModelProxy"
    var proxyModel = (new ProxyGenerator()).CreateClassProxy<SimpleViewModel>(); 
    proxyModel.ID = 1; 
    //Put it into List<> (it can handle a single item without issue!) 
    var list = new List<SimpleViewModel> { proxyModel }; 
    var serializer = new System.Runtime.Serialization.Json.DataContractJsonSerializer(typeof(List<SimpleViewModel>)); 
    using (var stringWriter = new MemoryStream()) 
    { 
        serializer.WriteObject(stringWriter, list); //BOOM CRASH! 
    } 
} 

Doing this gives me the following exception:

System.Runtime.Serialization.SerializationException : Type 'Castle.Proxies.SimpleViewModelProxy' with data contract name 'SimpleViewModelProxy: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.

I'm able to serialize either a single "SimpleViewModelProxy" object, or a List<SimpleViewModel>, but not a List<SimpleViewModelProxy>. Has anyone had any experience getting this to work? Can they provide some pointers on what I'm doing wrong?

Answer 1

You can try to add the type of the proxy to the list of known types:

var serializer = new DataContractJsonSerializer(
    typeof(List<SimpleViewModel>),
    new[] { proxyModel.GetType() });