//Return the value from registration.aspx.cs page
 return new JavaScriptSerializer().Serialize(new { jsonObject });

 //Receiving data here in ajax success
 $.ajax({
        type: "POST",
        contentType: "application/json; charset=utf-8",
        url: "http://localhost:28331/register/registration.aspx/verifyAadhar",
        data: verfAadhar,
        datatype: 'json',
        async: false,
        success: function (data) {

            var objData = jQuery.parseJSON(data);

            $("#fname").val(objData[4]);
        },
        error: function ()
        { console.log('Check your credentials'); }
    });