public ActionResult Edit(int?id, Software_Requirement model)
 {
     model.id = id ?? -1;
     try
     {
         if (id == null)
         {
             rs.InsertRequirement(model);
             return(RedirectToAction("Index"));
         }
         else
         {
             rs.UpdateRequirement(model);
             return(RedirectToAction("Details", new { id = model.id }));
         }
     }
     catch
     {
         return(View(model));
     }
 }