web service should return json

Question

I need my web service to return JSON...

I have the following code in my .asmx file:

namespace Feed
{
    [WebService(Namespace = "http://tempuri.org/")]
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
    [System.ComponentModel.ToolboxItem(false)]

    [System.Web.Script.Services.ScriptService]
    public class searchPerson : System.Web.Services.WebService
    {

        [WebMethod]
        [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
        public Person GetDave()
            {
                Person dave = new Person();

                dave.FirstName = "Dave";
                dave.LastName = "Ward";

         return dave;
        }
    }
}

Which returns the following:

<?xml version="1.0" encoding="utf-8"?>
<Person xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://tempuri.org/">
  <FirstName>Dave</FirstName>
  <LastName>Ward</LastName>
</Person>

How do I force it to return JSON instead of XML?

Answer 1

Your webservice definition looks correct. Ensure that you are calling the service through a post and remember that the key is specifying the 'content type' header as application/json.

(This is using jQuery but you could use low level javascript if you like)

$.ajax({
    type: "POST",
    contentType: "application/json; charset=utf-8;",
    url: "http://MyWebServiceURL",
    data: JSON.stringify({ ParameterName: "DataToSend" }),
    dataType: "json",
    success: function (data, textStatus, jqXHR) {
        //do something
    },
    error: function (jqXHR, textStatus, errorThrown) {
        //fail nicely
    }
});

Answer 2

Add the below referances before starting:

using System.Web.Script.Services;
using System.Web.Script.Serialization;

Use the below code in your method, for converting any data into JSON Data format in end:

JavaScriptSerializer serializer = new JavaScriptSerializer();
return serializer.Serialize(empData);

empData is array of DataRows from DataTable.