C# Web Service won't output JSON, only XML

Question

I'm trying to use jQuery and JSON with a C# Web Service that I wrote. No matter what, the following code will only output in XML.

Webservice Code

[WebMethod]
[ScriptMethod(ResponseFormat = ResponseFormat.Json)]
public string HelloWorld() {
    return "Hello World!";
}

I also have these attributes assigned to the class

[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
[ScriptService]

jQuery Code

$.ajax({
    type: "POST",
    contentType: "application/json; charset=utf-8",
    url: "ScheduleComputerDS.asmx/HelloWorld",
    data: "{}",
    dataType: "jsonp",
    success: function(data) {
        alert(data);
    }
});

The ASMX page always returns as content type "text/xml". Anything I'm missing?

EDITS: In response to a couple answers:

If I have the datatype as just "json" the content is still XML and jQuery also will not call my callback function. If I add the "&callback=?" to the url, IIS throws a HTTP 500 error.

My class does inherit from "System.Web.Services.WebService".

From doing some research on your guys answers, it looks like I do need to mess with WCF. Unfortunately the JSON that is returned is more designed for MS Ajax and is a lot of useless bloat for my use. I may look into an open source library like Jayrock or something similar.

Thanks for all your help!

Im new to Stackoverflow so I dont know how this comment is going to look in reference to the others but... If I have the datatype as just "json" the content is still XML and jQuery also will not call my callback function. If I add the "&callback=?" to the url, IIS throws a HTTP 500 error. — ajwdev
– ajwdev, Commented Mar 19, 2009 at 20:13
@TheDude - you can edit your original question to add this information in. There's an edit link under the tags on the bottom left of the question section — Russ Cam
– Russ Cam, Commented Mar 19, 2009 at 20:14
If you can use the WCF REST Starter Kit, just released a Preview 2 — bendewey
– bendewey, Commented Mar 19, 2009 at 20:15

eduncan911 · Accepted Answer · 2009-03-19 20:06:01Z

6

I think there's a typo:

dataType: "jsonp",

Should be:

dataType: "json",

answered Mar 19, 2009 at 20:06

eduncan911

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3 Comments

Simon_Weaver Over a year ago

awesome :) i made this mistake recently but i had "script" in there. was copied and pasted from an example

Luis Over a year ago

I know its an old post, I just wanna make sure that everyone new on this, dont fall on the wrong way, its jsonp no typo there, check json-p.org

eduncan911 Over a year ago

@LuisSánchez: jsonp is not recommended. leave it json. directly from that link you provided: "authors who rely on JSON-P for cross-domain Ajax are in fact opening themselves up to potentially just as much mayhem as was attempted to be avoided by implementing the same-origin policy in the first place"

Rob Windsor · Accepted Answer · 2009-03-19 20:13:50Z

3

As far as I know, the ScriptService attribute just allows the service to automatically create a JavaScript proxy (by appending /js to the endpoint address - ScheduleComputerDS.asmx/js in your case). It does not allow you to call the operations on the service the way you're trying to do.

You could instead use a RESTful WCF service (which requires .NET 3.5) which you can access by sending a properly shaped URI via an HTTP GET.

answered Mar 19, 2009 at 20:13

Rob Windsor

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Comments

bendewey · Accepted Answer · 2009-03-19 20:13:08Z

3

Rich Strahl has a really basic post that should help you out with this.

http://www.west-wind.com/weblog/posts/164419.aspx

answered Mar 19, 2009 at 20:13

bendewey

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1 Comment

ajwdev Over a year ago

This link was very helpful. Thank you

Russ Cam · Accepted Answer · 2009-03-19 20:26:48Z

1

Have you tried with datatype json?

Also, have a look at Encosia's Using jQuery to Consume ASP.NET JSON Web Services article on the matter. There's some good info on common pitfalls too.

edited Mar 19, 2009 at 20:26

answered Mar 19, 2009 at 20:05

Russ Cam

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