How do I access an ASP.NET variable to pass as JSON string to WCF Ajax Enabled Service

Question

I have a WCF AJAX enabled web service, and I am trying to pass a value of a field in an ASP.NET page into it with JSON but I always get nothing f. I want to do something like what we did in ASP.NET web services:

request.form("SbID").toString();

My Web Service is getting in a parameter that is NULL and I think its because of what I pass in the form. The Web Service is:

[OperationContract]
        [WebGet]
        public ResultData GetContactsDataAndCountbyGUID(string requestGUID)
        {
            ResultData result = new ResultData();
            common c = new common();

            string request = String.Empty;
            try
            {
                request = OperationContext.Current.RequestContext.RequestMessage.ToString();

            }
            catch (Exception ex)
            {

            }

            try
            {
                List<CONTACT> listContacts = new List<CONTACT>();

                DataSet ds = new DataSet();
                ds = c.GetDataSet(requestGUID);
                DataTable dt = new DataTable();
                dt = ds.Tables[0];

                // listContacts = CollectionHelper.ConvertTo<CONTACT>(dt);

                listContacts = c.ConvertTo<CONTACT>(dt);

                result.Data = listContacts;
                result.Count = listContacts.Count;

           }

This is the JavaScript/jQuery:

  <script type="text/javascript">
            //function DoUpdate(sbiId) {
            //    var input = '{"SbiId":"' + sbiId + '"}';
            //    var dataSource;
        $(document).ready(function() {
            **var input ='{"SbiId":"<%=guid %>"}';**
            $.ajax({
                url: "http://www.blah.com/services/testsService.svc/GetContactsDataAndCountbyGUID",
                type: "GET",
                contentType: "application/json; charset=utf-8",
                data: input,
                dataType: "json",
                success: function(data) {
                    var mtv = $find("<%= RadGrid1.ClientID %>").get_masterTableView();
                    console.log(data);
                    mtv.set_dataSource(data.d.Data);
                    mtv.dataBind();
                }
            });
            // }

        });
        </script>

I am trying to pass the value of GUID, which is in the form by:

public string guid = null;
        common c = new common();
        protected void Page_Load(object sender, EventArgs e)
        {
             try
            {

                IHubContext hubContext = GlobalHost.ConnectionManager.GetHubContext<AlphaHub>();
                // common c = new common();
                var userManager = new UserManager<ApplicationUser>(new UserStore<ApplicationUser>(new ApplicationDbContext()));
                ApplicationUser user = userManager.FindByNameAsync(User.Identity.Name).Result;
                string connectionId =  c.GetCurrentConnection(user.RegistrationCode);       

                string request = "Contact" + " - " + connectionId + " - " + user.RegistrationCode;
                string guid = c.recordDataRequest(user.RegistrationCode, request, connectionId, "out", "");
                request = request + " - " + guid;
                hubContext.Clients.Client(connectionId).CallForReport(request);  
           //   hub
                Thread.Sleep(1000);
            }

How do I get this value passed in and retrieved?

Answer 1

ASP.Net is stateless, you're not going to be able to access a variable from the code behind. Store it in a hidden variable which you can access from jQuery.

<input type="hidden" id="hdnGuid" runat="server">

Set it in your code behind:

string guid = c.recordDataRequest(user.RegistrationCode, request, connectionId, "out", "");
hdnGuid.Value = guid;

In your jQuery accesses it:

var hdnGuid = $("#<%= hdnGuid.ClientID %>").val();
var input ='{"SbiId":"' + hdnGuid + '"}';