Send large JSON data to WCF Rest Service

Question

Hi

I have a client web page that is sending a large json object to a proxy service on the same domain as the web page.

The proxy (an ashx handler) then forwards the request to a WCF Rest Service. Using a WebClient object (standard .net object for making a http request)

The JSON successfully arrives at the proxy via a jQuery POST on the client webpage.

However, when the proxy forwards this to the WCF service I get a Bad Request - Error 400

This doesn't happen when the size of the json data is small

The WCF service contract looks like this

[WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.Wrapped, RequestFormat = WebMessageFormat.Json, ResponseFormat = WebMessageFormat.Json)]
[OperationContract]
CarConfiguration CreateConfiguration(CarConfiguration configuration);

And the DataContract like this

[DataContract(Namespace = "")]
 public class CarConfiguration
 {
        [DataMember(Order = 1)]
        public int CarConfigurationId { get; set; }
        [DataMember(Order = 2)]
        public int UserId { get; set; }
        [DataMember(Order = 3)]
  public string Model { get; set; }
        [DataMember(Order = 4)]
        public string Colour { get; set; }
        [DataMember(Order = 5)]
        public string Trim { get; set; }
        [DataMember(Order = 6)]
        public string ThumbnailByteData { get; set; }
        [DataMember(Order = 6)]
        public string Wheel { get; set; }
        [DataMember(Order = 7)]
        public DateTime Date { get; set; }
  [DataMember(Order = 8)]
  public List<string> Accessories { get; set; }
  [DataMember(Order = 9)]
        public string Vehicle { get; set; }
  [DataMember(Order = 10)]
  public Decimal Price { get; set; }
 }

When the ThumbnailByteData field is small, all is OK. When it is large I get the 400 error

What are my options here?

I've tried increasing the MaxBytesRecived config setting but that is not enough

Any ideas?