asp.net asmx web service returning xml instead of json

Question

Why does this simple web service refuse to return JSON to the client?

Here is my client code:

        var params = { };
        $.ajax({
            url: "/Services/SessionServices.asmx/HelloWorld",
            type: "POST",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            timeout: 10000,
            data: JSON.stringify(params),
            success: function (response) {
                console.log(response);
            }
        });

And the service:

namespace myproject.frontend.Services
{
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]
    [ScriptService]
    public class SessionServices : System.Web.Services.WebService
    {
        [WebMethod]
        [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
        public string HelloWorld()
        {
            return "Hello World";
        }
    }
}

web.config:

<configuration>
    <system.web>
        <compilation debug="true" targetFramework="4.0" />
    </system.web>
</configuration>

And the response:

<?xml version="1.0" encoding="utf-8"?>
<string xmlns="http://tempuri.org/">Hello World</string>

No matter what I do, the response always comes back as XML. How do I get the web service to return Json?

EDIT:

Here is the Fiddler HTTP trace:

REQUEST
-------
POST http://myproject.local/Services/SessionServices.asmx/HelloWorld HTTP/1.1
Host: myproject.local
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20100101 Firefox/13.0.1
Accept: application/json, text/javascript, */*; q=0.01
Accept-Language: en-gb,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
Content-Type: application/json; charset=utf-8
X-Requested-With: XMLHttpRequest
Referer: http://myproject.local/Pages/Test.aspx
Content-Length: 2
Cookie: ASP.NET_SessionId=5tvpx1ph1uiie2o1c5wzx0bz
Pragma: no-cache
Cache-Control: no-cache

{}

RESPONSE
-------
HTTP/1.1 200 OK
Cache-Control: private, max-age=0
Content-Type: text/xml; charset=utf-8
Server: Microsoft-IIS/7.5
X-AspNet-Version: 4.0.30319
X-Powered-By: ASP.NET
Date: Tue, 19 Jun 2012 16:33:40 GMT
Content-Length: 96

<?xml version="1.0" encoding="utf-8"?>
<string xmlns="http://tempuri.org/">Hello World</string>

I have lost count of how many articles I have read now trying to fix this. The instructions are either incomplete or do not solve my issue for some reason. Some of the more relevant ones include (all without success):

• ASP.NET web service erroneously returns XML instead of JSON
• asmx web service returning xml instead of json in .net 4.0
• http://williamsportwebdeveloper.com/cgi/wp/?p=494
• http://encosia.com/using-jquery-to-consume-aspnet-json-web-services/
• http://forums.asp.net/t/1054378.aspx
• http://jqueryplugins.info/2012/02/asp-net-web-service-returning-xml-instead-of-json/

Plus several other general articles.

Kaolin

I see the target framework tag set to 4.0, what version of the framework is your app actually built in? – Daft

Under Project Properties on the Application tab, the Target Framework is ".Net Framework 4". Is that sufficient, or do I need to set it somewhere else? Sorry, I'm relatively new to VS (more js experience) – Kaolin

Your code looks correct. Would you please record your AJAX request and the server's reply using WireShark? It would be useful to see these HTTP packets to understand what happens. – Portly

@kol: Thanks for taking the time to look at this. I have posted the HTTP trace as requested. Maybe you can see something I'm missing. – Kaolin

Possible duplicate: #9915282 – Melliemelliferous

Answer 1

Finally figured it out.

The app code is correct as posted. The problem is with the configuration. The correct web.config is:

<configuration>
    <system.web>
        <compilation debug="true" targetFramework="4.0" />
    </system.web>
    <system.webServer>
        <handlers>
            <add name="ScriptHandlerFactory"
                 verb="*" path="*.asmx"
                 type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
                 resourceType="Unspecified" />
        </handlers>
    </system.webServer>
</configuration>

According to the docs, registering the handler should be unnecessary from .NET 4 upwards as it has been moved to the machine.config. For whatever reason, this isn't working for me. But adding the registration to the web.config for my app resolved the problem.

A lot of the articles on this problem instruct to add the handler to the <system.web> section. This does NOT work and causes a whole load of other problems. I tried adding the handler to both sections and this generates a set of other migration errors which completely misdirected my troubleshooting.

In case it helps anyone else, if I had ther same problem again, here is the checklist I would review:

1. Did you specify type: "POST" in the ajax request?
2. Did you specify contentType: "application/json; charset=utf-8" in the ajax request?
3. Did you specify dataType: "json"in the ajax request?
4. Does your .asmx web service include the [ScriptService] attribute?
5. Does your web method include the [ScriptMethod(ResponseFormat = ResponseFormat.Json)] attribute? (My code works even without this attribute, but a lot of articles say that it is required)
6. Have you added the ScriptHandlerFactory to the web.config file in <system.webServer><handlers>?
7. Have you removed all handlers from the the web.config file in in <system.web><httpHandlers>?

Hope this helps anyone with the same problem. and thanks to posters for suggestions.

Kaolin

I have been beating my head against the wall for quite a few hours on this and your post has been so very helpful. I have run through all seven steps and my service is still returning xml in the response. I am using ASP.NET 3.5 - any other thoughts? I am also using the jQuery form plugin (not need to explicitly state POST, json, etc.) – Desalvo

If you open a new question and add a comment here linking to it, I can take a look. Please include a fiddler trace of the request and the response. Include your complete web.config. And also include the asp.net code specifically including attributes. I suggest you test using a similar "Hello World" service as per my example. – Kaolin

This answer helped me a lot, especially the seven steps he mentioned. – Disaccustom

i'm using this same in my application but i'm getting an error, can you please suggest me what i'm missing here. XMLHttpRequest cannot load 192.168.200.56/ChatApp.asmx/HelloWorld. Invalid HTTP status code 500 – Herbst

Adding some more magic for #2, changing contentType to just "application/json" solved my problem. – Blasted

Answer 2

No success with above solution, here how I resolved it.

put this line into your webservice and rather return type just write the string in response context

this.Context.Response.ContentType = "application/json; charset=utf-8";
this.Context.Response.Write(serial.Serialize(city));

Tonus

You did it! This is the best answer. I made my function a "void" return-type and used your code, and JQuery UI autocomplete starts working finally. – Alitaalitha

That's crude and worrying, but brutally effective when the more complicated mucking about doesn't seem to solve my problem. This works. – Ealasaid

Happy bunny! :D – Dalton

Dude, your my best savior ever! I've been beating my head against the wall for many hours until I saw your answer, nothing else has helped me. I just love you so much :) – Libya

Answer 3

If you want to stay remain with Framework 3.5, you need to make change in code as follows.

[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 
[ScriptService]
public class WebService : System.Web.Services.WebService
{
    public WebService()
    {
    }

    [WebMethod]
    public void HelloWorld() // It's IMP to keep return type void.
    {
        string strResult = "Hello World";
        object objResultD = new { d = strResult }; // To make result similarly like ASP.Net Web Service in JSON form. You can skip if it's not needed in this form.

        System.Web.Script.Serialization.JavaScriptSerializer ser = new System.Web.Script.Serialization.JavaScriptSerializer();
        string strResponse = ser.Serialize(objResultD);

        string strCallback = Context.Request.QueryString["callback"]; // Get callback method name. e.g. jQuery17019982320107502116_1378635607531
        strResponse = strCallback + "(" + strResponse + ")"; // e.g. jQuery17019982320107502116_1378635607531(....)

        Context.Response.Clear();
        Context.Response.ContentType = "application/json";
        Context.Response.AddHeader("content-length", strResponse.Length.ToString());
        Context.Response.Flush();

        Context.Response.Write(strResponse);
    }
}

Spermato

It would be helpful if you added to your answer what you have used and possibly link to the documentation. That way it is a lot easier for someone else to figure out how this exactly works and how they can use it in an other situation. – Deca

This answer works good for ASMX + jQuery in Sharepoint 2010 and .NET Framework 3.5. I decided to use standard JavaScriptSerializer instead of reference to NewtonJson assembly. Thanks! – Donatello

Answer 4

There is much easier way to return a pure string from web service. I call it CROW function (makes it easy to remember).

  [WebMethod]
  public void Test()
    {
        Context.Response.Output.Write("and that's how it's done");    
    }

As you can see, return type is "void", but CROW function will still return the value you want.

Leary

This worked perfectly for me. I changed my string return to a void and used the context.response.output.write to spit out the JSON that was serialized! – Ragg

Answer 5

I have a .asmx web service (.NET 4.0) with a method that returns a string. The string is a serialized List like you see in many of the examples. This will return json that is not wrapped in XML. No changes to web.config or need for 3rd party DLLs.

var tmsd = new List<TmsData>();
foreach (DataRow dr in dt.Rows)
{

m_firstname = dr["FirstName"].ToString();
m_lastname = dr["LastName"].ToString();

tmsd.Add(new TmsData() { FirstName = m_firstname, LastName = m_lastname} );

}

var serializer = new System.Web.Script.Serialization.JavaScriptSerializer();
string m_json = serializer.Serialize(tmsd);

return m_json;

The client part that uses the service looks like this:

   $.ajax({
       type: 'POST',
       contentType: "application/json; charset=utf-8",
       dataType: 'json',
       url: 'http://localhost:54253/TmsWebService.asmx/GetTombstoneDataJson',
       data: "{'ObjectNumber':'105.1996'}",
       success: function (data) {
           alert(data.d);
       },
       error: function (a) {
           alert(a.responseText);
       }
   });

Arrhythmia

Answer 6

Hope this helps, it appears that you still have to send some JSON object in the request, even if the Method you are calling has no parameters.

var params = {};
return $http({
        method: 'POST',
        async: false,
        url: 'service.asmx/ParameterlessMethod',
        data: JSON.stringify(params),
        contentType: 'application/json; charset=utf-8',
        dataType: 'json'

    }).then(function (response) {
        var robj = JSON.parse(response.data.d);
        return robj;
    });

Buckden

Answer 7

For me it works with this code I got from this post:

How can I return json from my WCF rest service (.NET 4), using Json.Net, without it being a string, wrapped in quotes?

[WebInvoke(UriTemplate = "HelloWorld", Method = "GET"), OperationContract]
public Message HelloWorld()
{
    string jsonResponse = //Get JSON string here
    return WebOperationContext.Current.CreateTextResponse(jsonResponse, "application/json; charset=utf-8", Encoding.UTF8);
}

Phosphatase

The ScriptService attribute should take care of this automatically. I really don't want to handle all the serialization stuff myself. I have other projects where this code works just fine. But they're on other servers, which makes me think there is some kind of configuration issue. – Kaolin

Answer 8

I have tried all of the above steps ( even the answer), but i was not successful, my system configuration is Windows Server 2012 R2, IIS 8. The following step solved my problem.

Changed the app pool, that has managed pipeline = classic.

Clareclarence

Answer 9

I know that is really old question but i came to same problem today and I've been searching everywhere to find the answer but with no result. After long research I have found the way to make this work. To return JSON from service you have provide data in request in the correct format, use JSON.stringify() to parse the data before request and don't forget about contentType: "application/json; charset=utf-8", using this should provide expected result.

Reparative

Answer 10

response = await client.GetAsync(RequestUrl, HttpCompletionOption.ResponseContentRead);
if (response.IsSuccessStatusCode)
{
    _data = await response.Content.ReadAsStringAsync();
    try
    {
        XmlDocument _doc = new XmlDocument();
        _doc.LoadXml(_data);
        return Request.CreateResponse(HttpStatusCode.OK, JObject.Parse(_doc.InnerText));
    }
    catch (Exception jex)
    {
        return Request.CreateResponse(HttpStatusCode.BadRequest, jex.Message);
    }
}
else
    return Task.FromResult<HttpResponseMessage>(Request.CreateResponse(HttpStatusCode.NotFound)).Result;

Unwearied