title: web service returning xml although return format is json
body: <p>Here is the web service</p>
  
  <pre><code>public class HelloWorld : System.Web.Services.WebService
  {
  
      [WebMethod]
      [ScriptMethod(ResponseFormat = ResponseFormat.Json)]
      public string Hello()
      {
          return "Hello World";
      }
  }
  </code></pre>
  
  <p>Here is the javascript ajax code</p>
  
  <pre><code> $(document).ready(function () {
          $.ajax({
              url: "Service/HelloWorld.asmx/Hello",
              dataType: 'json',
              type: 'POST',
              cache: false,
              crossDomain: true,
              timeout: 15000,
              success: function (rtndata) {
                  alert('Success : :' + rtndata);
              },
              error: function (xhr, errorType, exception) {
                  alert("Excep:: " + exception + "Status:: " + xhr.statusText);
              }
          });
      });
  </code></pre>
  
  <p>Getting error </p>
  
  <pre><code>    Excep:: Invalid JSON: &lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;string xmlns="http://tempuri.org/"&gt;Hello World&lt;/string&gt;Status:: OK 
  </code></pre>