public JsonResult UnassignTest(int userId, int testId)
 {
     var common = new CommonService();
     common.OnRenderPartialViewToString += (model) =>
     {
         var result = string.Empty;
         try
         {
             result = this.RenderPartialViewToString("P_Assign_Test_To_Student", model);
         }
         catch (Exception)
         {
             common.success = false;
             common.message = Constants.DefaultExceptionMessage;
         }
         return result;
     };
     common.UnassignTest(userId, testId);
     return Json(new { common.success, common.message ,common.generatedHtml});
 }