How to return JSON from a 2.0 asmx web service

Question

I saw another question like this but it did not answer my question. I am using .Net framework 2.0 / jQuery to make an Ajax call to a 2.0 web service. No matter what I set the contentType to in the ajax call, the service always returns XML. I want it to return Json!

Here is the call:

      $(document).ready(function() {
         $.ajax({
      type: "POST",
      url: "DonationsService.asmx/GetDate",
      data: "{}",
      contentType: "application/json; charset=utf-8",
      dataType: "json",
      success: function(msg) {
        // Hide the fake progress indicator graphic.
        $('#RSSContent').removeClass('loading');

        // Insert the returned HTML into the <div>.
        $('#RSSContent').html(msg.d);
      }
       });
     });

Here is what the request header looks like in Fiddler:

POST /DonationsService.asmx/GetDate HTTP/1.1
x-requested-with: XMLHttpRequest
Accept-Language: en-us
Referer: http://localhost:1238/text.htm
Accept: application/json, text/javascript, */*
Content-Type: application/json; charset=utf-8
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322; eMusic DLM/4; .NET CLR 2.0.50727)
Host: localhost:1238
Content-Length: 2
Connection: Keep-Alive
Pragma: no-cache

I have tried setting the contentType to 'text/json' and get the same results.

Here is the web service method:

<WebMethod()> _
Public Function GetDate() As String

 'just playing around with Newtonsoft.Json
 Dim sb As New StringBuilder
 Dim sw As New IO.StringWriter(sb)
 Dim strOut As String = String.Empty

 Using jw As New JsonTextWriter(sw)
  With jw
   .WriteStartObject()
   .WritePropertyName("DateTime")
   .WriteValue(DateTime.Now.ToString)
   .WriteEndObject()
  End With
  strOut = sw.ToString
 End Using

 Return strOut

End Function

and here is what it returns:

<?xml version="1.0" encoding="utf-8"?>
<string xmlns="http://DMS.Webservices.org/"&gt;{"DateTime":"11/13/2008 6:04:22 PM"}</string>

Does anyone know how to force the web service to return Json when I ask for Json?

Please don't tell me to upgrade to .Net Framework 3.5 or anything like that (I'm not that stupid). I need a 2.0 solution.

Thanks

Answer 1

You probably can't do anything other than XML or binary serialization in .NET 2.0. If you're not using an autogenerated web reference then don't bother with ASMX. Just use an ASPX or ASHX instead.

Answer 2

I may not be 100% correct on this but I'm sure .net webservices are XML/SOAP based.

You would need to override the default behavior of the webservice. I'm not entirely sure that this would even be possible.

I know this won't be the most useful answer, but may get you headed in the right direction.

Answer 3

See the answers to my question:

ASP.NET - What is the correct approach to JSON based web services with jQuery?

Answer 4

You need to decorate your web method with the following:

[ScriptMethod(ResponseFormat = ResponseFormat.Json)]

You've got the rest right :)

More info at Encosia and Andrew Roland's Blog

EDIT: As noted below this is .NET 3.5 only (I was unaware of this, my bad).

Answer 5

You can use the Jayrock library Quick start for asp.net

This allows you to write a http handler to return you json.

<%@ WebHandler Class="JayrockWeb.HelloWorld" %>

namespace JayrockWeb
{
    using System;
    using System.Web;
    using Jayrock.Json;
    using Jayrock.JsonRpc;
    using Jayrock.JsonRpc.Web;

    public class HelloWorld : JsonRpcHandler
    {
        [ JsonRpcMethod("greetings") ]
        public string Greetings()
        {
            return "Welcome to Jayrock!";
        }
    }
}

Answer 6

It's no problem to return JSON from ASMX services in ASP.NET 2.0. You just need the ASP.NET AJAX Extensions installed.

Do be sure to add the [ScriptService] decoration to your web service. That's what instructs the server side portion of the ASP.NET AJAX framework to return JSON for a properly formed request.

Also, you'll need to drop the ".d" from "msg.d" in my example, if you're using it with 2.0. The ".d" is a security feature that came with 3.5.