How to set Json.Net as the default serializer for WCF REST service

Solution 1:

The usage of Extending Encoders and Serializers (see http://msdn.microsoft.com/en-us/library/ms733092.aspx) or other methods of Extending WCF like usage of DataContractSerializerOperationBehavior is very interesting, but for your special problem there are easier solution ways.

If you already use Message type to return the results an use WCF4 you can do something like following:

public Message UpdateCity(string code, City city)
{
    MyResponseDataClass message = CreateMyResponse();
    // use JSON.NET to serialize the response data
    string myResponseBody = JsonConvert.Serialize(message);
    return WebOperationContext.Current.CreateTextResponse (myResponseBody,
                "application/json; charset=utf-8",
                Encoding.UTF8);
}

In case of errors (like HttpStatusCode.Unauthorized or HttpStatusCode.Conflict) or in other situations when you need to set a HTTP status code (like HttpStatusCode.Created) you can continue to use WebOperationContext.Current.OutgoingResponse.StatusCode.

As an alternative you can also return a Stream (see http://blogs.msdn.com/b/carlosfigueira/archive/2008/04/17/wcf-raw-programming-model-web.aspx and http://msdn.microsoft.com/en-us/library/ms732038.aspx) instead of Message to return any data without additional default processing by Microsoft JSON serializer. In case of WCF4 you can use CreateStreamResponse (see http://msdn.microsoft.com/en-us/library/dd782273.aspx) instead of CreateTextResponse. Don't forget to set stream position to 0 after writing in the stream if you will use this technique to produce the response.

Solution 2:

Is there some reason why you want to use the Json.NET library specifically. If you want to return JSON, why not just use the ResponseFormat property from the WebGet and WebInvoke attributes?

[WebGet(UriTemplate = "", ResponseFormat = WebMessageFormat.Json)]

That should for most cases. What version of WCF are you running? Any reason you're returning a Message type rather than the actual type?