get JSON from ASP.NET web service ASMX file

Question

I'm creating a web service using ASP.NET, C#, currently it is giving XML, but I'm going to get JSON, this is how I create my webmtheod:

[Webservice(Namespace="http://myurl)]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfiles_1)]
[System.ComponentModel.ToolboxItem(false)]

[WebMehod]
public string myfunction()
{

string r = "......";


return r;
}

these are in an ASMX file, which I call it in my browser

this function returns me XML output but I'm going to get JSON, how can I get JSON? I think I should use .NET serialization functions, but how? — Ali_dotNet, Nov 20 '12 at 14:09

Darren Wainwright · Accepted Answer · 2012-11-20T14:39:24.740

If you want to return JSON from your method you will need to use the ScriptMethod attribute.

Structure your method like this, notice the [ScriptMethod(ResponseFormat = ResponseFormat.Json)] attribute.

    [WebMethod()]
    [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
    public string MyMethod()
    {

    }

At the moment, this method is returning a string, which can be a JSON structured string. However, you may be better to return an object, which can be parsed as JSON. List<string> as well as Class's with standard data-types, like integers, strings etc are great for this. You can then return just that object. the ScriptMethod takes care of transforming it into JSON.

For example:

The Class you want to return:

      public class MyJson
      {
         public int ID;
         public List<string> SomeList;
         public string SomeText;
     }

And your method to return a populated MyJson

        [WebMethod()]
        [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
        public MyJson MyMethod()
        { 
          MyJson m = new MyJson();
          m.ID = 1;
          m.SomeText = "Hello World!";
          m.SomeList = new List<string>();
          m.SomeList.Add("Foo");
          m.SomeList.Add("Bar");

          return m;
        }

The return JSON will be structured just like the class. The property names will be used too, and your List<string> will become an array

Call this using AJAX. JQuery in this case:

$(document).ready(function(){

      $.ajax({
            type: "POST",
            url: "/YourPage.aspx/MyMethod",
            data: "{}",
            contentType: "application/json; charset=utf-8",
            dataType: "json",
            success: function (msg) {

             // content will be in here... I.E
             var id = msg.d.ID;
             var st = msg.d.SomeText;
             var sl = msg.d.SomeList;
             var i = sl.length;
            var firstSlItem = sl[0];
            }
        });
});

thanks, but it seems that I'm still getting an XML (it is now structured like my class), how should I call my webservice in my browser to get json output? — Ali_dotNet, Nov 20 '12 at 14:29
Call it with AJAX, making sure to specify the Datatype as JSON. I will add some example code. — Darren Wainwright, Nov 20 '12 at 14:36
If it's still returning AJAX then see this page http://stackoverflow.com/questions/2749954/asmx-web-service-returning-xml-instead-of-json-in-net-4-0 - don't forget to mark all as answered if they help, and upvote other answers if they help you too. — Darren Wainwright, Nov 20 '12 at 14:43

score 2 · Answer 2 · answered Aug 01 '13 at 02:51

An alternate approach would be to use JavaScriptSerializer to return JSON as a string:

[System.Web.Services.WebMethod()]
public string GetItems() {
    List<string> listOfItems = new List<string> {"asdf", "qwerty", "abc", "123"};

    JavaScriptSerializer js = new JavaScriptSerializer();
    string json = js.Serialize(listOfItems);

    return json;
}

...be sure to use this import:

using System.Web.Script.Serialization;

...and you will then have to parse the result in javascript / jQuery like this:

var result = "";

$.ajax({

      // ...other properties defined here...

      success: function (response) {
            result = JSON.parse(response.d);
      }
});

// the List<string> has been parsed into an array:
for (var i = 0, len = result.length; i < len; i++) {
      alert(result[i]);
}

If you convert an instance of a class in this same way, such as @Darren's example here, it will then be parsed as a javascript object-literal.

Also note that in an .asmx file webmethods are declared as public instance methods, as opposed to public static in .aspx files.

get JSON from ASP.NET web service ASMX file

2 Answers2