public ActionResult Index(CalcModel model)
        {
            model.OperationList = Calc.Operations
                                  .Select(o => new SelectListItem()
            {
                Text = $"{o.Name}", Value = $"{o.Name}", Selected = model.Operation == o.Name
            });

            var operation = Calc.Operations.FirstOrDefault(o => o.Name == model.Operation);

            if (operation != null)
            {
                var dbOper    = OperationRepository.GetByName(operation.Name);
                var operId    = dbOper.Id;
                var inputData = string.Join(",", model.Arguments);

                var oldResult = ORRepository.GetOldResult(operId, inputData);
                if (!double.IsNaN(oldResult))
                {
                    model.Result = oldResult;
                }
                else
                {
                    #region вычисление
                    model.Result = operation.Execute(model.Arguments);

                    var rec = ORRepository.Create();

                    //текущего пользователя назначаем автором
                    var currUser = UserRepository.GetByName(User.Identity.Name);
                    rec.Author        = currUser;
                    rec.Operation     = dbOper;
                    rec.ExecutionDate = DateTime.Now;
                    rec.ExecutionTime = new Random().Next(0, 100);
                    rec.InputData     = inputData;
                    rec.Result        = model.Result ?? Double.NaN;

                    ORRepository.Update(rec);
                    #endregion
                }
                return(View(model));
            }
            return(View());
        }