asmx web service returning xml instead of json in .net 4.0

Question

i have just upgraded a test copy of my site to asp.net 4.0 and have noticed a strange issue that only arises when i upload the site to my server.

the site has an asmx web service that returns json, yet when i run the site on my server it returns xml. it as been working fine in asp.net 3.5 for over a year.

the webMethod is decorated with the correct attributes...

[WebMethod][ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public List<LocationRecentChange> RecentChanges()

and on my local machine it returns json.

yet on the server (Windows 2008 64bit) it returns xml.

using firebug console you will see a 200 OK response and a bunch of XML, and on my local machine the data returned is the JSON i expect.

Here is the javascript that calls the service..

function loadRecentData() {
$.ajax({
    type: "POST",
    url: "service/spots.asmx/RecentChanges",
    data: "{}",
    contentType: "application/json; charset=utf-8",
    dataType: "json",
    success: loadRecentUpdates,
    failure: function(msg) {
        //alert(msg);
    }
});

}

Any suggestions welcome, this has got me stumped!

Answer 1

Are you sure .NET 4 is installed on your server?

The ScriptHandlerFactory's "type" string in .NET 4 is:

System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"

ASP.NET 4 now includes that in its default web.config at the machine level. So, you shouldn't need any mapping to the ScriptHandlerFactory in your project's web.config, 3.5 or 4.

Answer 2

well i managed to track it down by reading up about ajax web services requests are handled here...

http://www.asp.net/%28S%28ywiyuluxr3qb2dfva1z5lgeg%29%29/learn/ajax/tutorial-05-cs.aspx

basically a handler from asp.net 3.5 needs to be declared in your web.config handlers section under system.webserver so that it can return a JSON response instead of the default.

here is what you need to add to the web.config handlers section (also add to httpHandlers section if you need to support IIS6)...

<handlers>
   <add name="ScriptHandlerFactory" verb="*" path="*.asmx" preCondition="integratedMode" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

i have my suspicions that this will need replacing with a .net 4.0 version of the same handler, but for now, it works.