$.ajax({
         type: "get", url: "street", data: { a: value2 },
         success: function (data) {

          alert(data);

                              }

[HttpGet]
        public string street(string a)
        {

            EmlakServicesClient client = new EmlakServicesClient();
            client.ClientCredentials.UserName.UserName = "service_test";
            client.ClientCredentials.UserName.Password = "..";
            client.ClientCredentials.ServiceCertificate.Authentication.CertificateValidationMode = System.ServiceModel.Security.X509CertificateValidationMode.None;
            Street[] list =client.GetStreet(Convert.ToInt32(a));

                   return ("" + list.FirstOrDefault().StreetName);


        }

return Json(list, JsonRequestBehavior.AllowGet);

public ActionResult GetsomeItems(int someId)
{
  var someCollection=GetListOfItemsFromSomeWhere(someId)
  return Json(someCollection,JsonRequestBehaviour.AllowGet);
}