JSON response from WCF escapes name values - json

Question

I am trying to return a dictionary from a WCF REST service as a JSON object. I want the format to be
{"key": "value"}
so I have created my own class as described here and here.
The service method works, sort of. The problem is that the key names are escaped. For example, if my dictionary contains "Hello world": 100, I get
{"Hello_x0020_world":100}. It also escapes other characters like %, etc.
Is there some way I can tell the serialization not to escape the names that way? It is almost like it is using xml rules that don't (necessarily) apply to JSON.
My serializable class:
[Serializable]
public class JsonDictionary : ISerializable
{
private Dictionary<string, object> _Dictionary;
public JsonDictionary()
{
_Dictionary = new Dictionary<string, object>();
}
public JsonDictionary(SerializationInfo info, StreamingContext context)
{
_Dictionary = new Dictionary<string, object>();
SerializationInfoEnumerator enumerator = info.GetEnumerator();
while (enumerator.MoveNext())
{
_Dictionary.Add(enumerator.Name, enumerator.Value);
}
}
public object this[string key]
{
get { return _Dictionary[key]; }
set { _Dictionary[key] = value; }
}
public void Add(string key, object value)
{
_Dictionary.Add(key, value);
}
public bool ContainsKey(string key)
{
return _Dictionary.ContainsKey(key);
}
public void GetObjectData(SerializationInfo info, StreamingContext context)
{
foreach (string key in _Dictionary.Keys)
info.AddValue(key, _Dictionary[key], _Dictionary[key] == null ? typeof(object) : _Dictionary[key].GetType());
}
}
My service function definition:
[WebGet(UriTemplate = "", ResponseFormat = WebMessageFormat.Json)]
public JsonDictionary GetCollection()
{
JsonDictionary dict = new JsonDictionary();
dict.Add("Hello world", 100);
return dict;
}

Answer 1

The DataContractJsonSerializer used by default in WCF uses a XML-to-JSON mapping which causes some issues, like the one you see in ISerializable types. You can, however, use a custom formatter to change how the response will be serialized. In the example below, I'm using JSON.NET which deals with ISerializable objects "correctly".
public class StackOverflow_16674152
{
[Serializable]
public class JsonDictionary : ISerializable
{
private Dictionary<string, object> _Dictionary;
public JsonDictionary()
{
_Dictionary = new Dictionary<string, object>();
}
public JsonDictionary(SerializationInfo info, StreamingContext context)
{
_Dictionary = new Dictionary<string, object>();
SerializationInfoEnumerator enumerator = info.GetEnumerator();
while (enumerator.MoveNext())
{
_Dictionary.Add(enumerator.Name, enumerator.Value);
}
}
public object this[string key]
{
get { return _Dictionary[key]; }
set { _Dictionary[key] = value; }
}
public void Add(string key, object value)
{
_Dictionary.Add(key, value);
}
public bool ContainsKey(string key)
{
return _Dictionary.ContainsKey(key);
}
public void GetObjectData(SerializationInfo info, StreamingContext context)
{
foreach (string key in _Dictionary.Keys)
info.AddValue(key, _Dictionary[key], _Dictionary[key] == null ? typeof(object) : _Dictionary[key].GetType());
}
}
[ServiceContract]
public class Service
{
[WebGet(UriTemplate = "", ResponseFormat = WebMessageFormat.Json)]
[MyISerializableResponseJsonBehavior]
public JsonDictionary GetCollection()
{
JsonDictionary dict = new JsonDictionary();
dict.Add("Hello world", 100);
return dict;
}
}
public class MyFormatter : IDispatchMessageFormatter
{
IDispatchMessageFormatter original;
string replyAction;
public MyFormatter(IDispatchMessageFormatter original, string replyAction)
{
this.original = original;
this.replyAction = replyAction;
}
public void DeserializeRequest(Message message, object[] parameters)
{
this.original.DeserializeRequest(message, parameters);
}
public Message SerializeReply(MessageVersion messageVersion, object[] parameters, object result)
{
ISerializable serializable = result as ISerializable;
if (serializable != null)
{
string json = JsonConvert.SerializeObject(serializable);
byte[] bytes = Encoding.UTF8.GetBytes(json);
var writer = new MyRawWriter(bytes);
Message reply = Message.CreateMessage(messageVersion, replyAction, writer);
reply.Properties.Add(WebBodyFormatMessageProperty.Name, new WebBodyFormatMessageProperty(WebContentFormat.Raw));
return reply;
}
else
{
return this.original.SerializeReply(messageVersion, parameters, result);
}
}
class MyRawWriter : BodyWriter
{
byte[] data;
public MyRawWriter(byte[] data)
: base(true)
{
this.data = data;
}
protected override void OnWriteBodyContents(XmlDictionaryWriter writer)
{
writer.WriteStartElement("Binary");
writer.WriteBase64(data, 0, data.Length);
writer.WriteEndElement();
}
}
}
public class MyISerializableResponseJsonBehaviorAttribute : Attribute, IOperationBehavior
{
public void AddBindingParameters(OperationDescription operationDescription, BindingParameterCollection bindingParameters)
{
}
public void ApplyClientBehavior(OperationDescription operationDescription, ClientOperation clientOperation)
{
}
public void ApplyDispatchBehavior(OperationDescription operationDescription, DispatchOperation dispatchOperation)
{
if (operationDescription.Messages.Count > 1)
{
dispatchOperation.Formatter = new MyFormatter(dispatchOperation.Formatter, operationDescription.Messages[1].Action);
}
}
public void Validate(OperationDescription operationDescription)
{
if (operationDescription.Messages.Count > 1)
{
var respMessage = operationDescription.Messages[1];
if (respMessage.Body.Parts.Count > 0)
{
throw new InvalidOperationException("Cannot be used with out/ref parameters");
}
}
var wga = operationDescription.Behaviors.Find<WebGetAttribute>();
var wia = operationDescription.Behaviors.Find<WebInvokeAttribute>();
WebMessageBodyStyle bodyStyle = WebMessageBodyStyle.Bare; // default
if (wga != null && wga.IsBodyStyleSetExplicitly) {
bodyStyle = wga.BodyStyle;
}
if (wia != null && wia.IsBodyStyleSetExplicitly) {
bodyStyle = wia.BodyStyle;
}
if (bodyStyle == WebMessageBodyStyle.Wrapped || bodyStyle == WebMessageBodyStyle.WrappedResponse)
{
throw new InvalidOperationException("This behavior can only be used with bare response style");
}
}
}
public static void Test()
{
string baseAddress = "http://" + Environment.MachineName + ":8000/Service";
ServiceHost host = new ServiceHost(typeof(Service), new Uri(baseAddress));
host.AddServiceEndpoint(typeof(Service), new WebHttpBinding(), "").Behaviors.Add(new WebHttpBehavior());
host.Open();
Console.WriteLine("Host opened");
WebClient c = new WebClient();
Console.WriteLine(c.DownloadString(baseAddress + "/"));
}
}