Returning raw json (string) in wcf

Question

I want to build my own JSON, and have the service return a string, here is the code

[OperationContract]
[WebInvoke(Method = "POST", BodyStyle = WebMessageBodyStyle.Bare, ResponseFormat = WebMessageFormat.Json)]
public string GetCurrentCart()
{
    //Code ommited
    string jsonClient = null;
    var j = new { Content = response.Content, Display=response.Display, SubTotal=response.SubTotal};
    var s = new JavaScriptSerializer();
    jsonClient = s.Serialize(j);
    return jsonClient;
}

The response I am getting contains the \" used to create "'s in strings in c#.

The following is the response.

"{\"Content\":\"\\r\\n\\u003cdiv\\u003e\\r\\n\\u003cinput type=\\\"hidden\\\" name=\\\"__VIEWSTATE\\\" id=\\\"__VIEWSTATE\\\" value=\\\"\/wEPDwUBMA9kFgJmD2QWAmYPZBYGAgMPFgIeBFRleHQFKFlvdSBoYXZlIG5vIGl0ZW1zIGluIHlvdXIgc2hvcHBpbmcgY2FydC5kAgUPFgIeB1Zpc2libGVoZAIHDxQrAAIPFgIfAWhkZGQYAQUMY3RsMDEkbHZDYXJ0D2dkoWijqBUJaUxmDgFrkGdWUM0mLpgQmTOe8R8hc8bZco4=\\\" \/\\u003e\\r\\n\\u003c\/div\\u003e\\r\\n\\r\\n\\u003cdiv class=\\\"block block-shoppingcart\\\"\\u003e\\r\\n    \\u003cdiv class=\\\"title\\\"\\u003e\\r\\n        \\u003cspan\\u003eShopping Cart\\u003c\/span\\u003e\\r\\n    \\u003c\/div\\u003e\\r\\n    \\u003cdiv class=\\\"clear\\\"\\u003e\\r\\n    \\u003c\/div\\u003e\\r\\n    \\u003cdiv class=\\\"listbox\\\"\\u003e\\r\\n        You have no items in your shopping cart.\\r\\n        \\r\\n        \\r\\n    \\u003c\/div\\u003e\\r\\n\\u003c\/div\\u003e\\r\\n\",\"Display\":\"You have no items in your shopping cart.\",\"SubTotal\":null}"

The values are being correctly encoded, but the json itself is not properly formatted. These \'s cause it to go out of wack.

How do I return a string without the \'s in front of the "'s?

Answer 1

Currently your web method returns a String together with ResponseFormat = WebMessageFormat.Json. It follows that your code will use the JSON encoding of the string. Corresponding to json.org, this means all double quotes in the string will be escaped using backslashes. So you currently have double JSON encoding.

The easiest way to return any kind of data is to change the output type of the GetCurrentCart() web method to Stream or Message (from System.ServiceModel.Channels) instead of String.

For code examples, see also...

• Carlos Figueira MSDN blog post, 'WCF "Raw" programming model',
• MSDN's "How to: Enable Streaming", and
• MSDN's "How to: Create a Service That Returns Arbitrary Data Using The WCF REST Programming Model".

Because you don't include in your question which version of .NET you use, I suggest you to use a universal (and the easiest) way:

public Stream GetCurrentCart()
{
    //Code ommitted
    var j = new { Content = response.Content, Display=response.Display,
                  SubTotal=response.SubTotal};
    var s = new JavaScriptSerializer();
    string jsonClient = s.Serialize(j);
    WebOperationContext.Current.OutgoingResponse.ContentType =
        "application/json; charset=utf-8";
    return new MemoryStream(Encoding.UTF8.GetBytes(jsonClient));
}

Answer 2

I tried the method suggested by Oleg but found that when i used this method for a large amount of data null key word was appended at the end of the JSON string.

Example: for json with lots of data {"JsonExample":"xxxxx"}null

found a solution to address this problem at : http://wcf.codeplex.com/workitem/67 Wrote the following function which will accept a object and return a Pure Json output. So before returning my object in the main method i make a call to the below method.

  public HttpResponseMessage ReturnPureJson(object responseModel)
    {
        HttpResponseMessage response = new HttpResponseMessage();

        string jsonClient = Json.Encode(responseModel);
        byte[] resultBytes = Encoding.UTF8.GetBytes(jsonClient);
        response.Content = new StreamContent(new MemoryStream(resultBytes));
        response.Content.Headers.ContentType = new MediaTypeHeaderValue("text/plain");

        return response;
    }

Answer 3

I recommend to use Jil library to Serialize your JSON object or dynamic(ExpandoObject).

In my case, It will avoid some null value problem, like always get "{}" from JsonConvert.SerializeXXX and extend {aa:bb} to {key:aa, value:bb} from JavaScriptSerializer

full sample here as below.

Interface:

[OperationContract]
[WebInvoke(Method = "POST", ResponseFormat = WebMessageFormat.Json, BodyStyle = WebMessageBodyStyle.Bare, UriTemplate = "json/GetCurrentCart")]
Stream GetCurrentCart(MyRequestParam Param);

Implementation:

public Stream GetCurrentCart(MyRequestParam Param)
{
    //code omitted
    dynamic j = new System.Dynamic.ExpandoObject();
    j.Content = response.Content;
    j.Display = response.Display; 
    j.SubTotal = response.SubTotal;
    string s = Jil.JSON.SerializeDynamic(j);
    WebOperationContext.Current.OutgoingResponse.ContentType = "application/json; charset=utf-8";
    return new MemoryStream(Encoding.UTF8.GetBytes(s));
} 

Answer 4

That was great (Oleg Response) and all make sure that you add the line WebOperationContext.Current.OutgoingResponse.ContentType = "application/json; charset=utf-8";

if you removed it result will be downloaded as file .