public ActionResult Manual() { if (this.Request.Method.Equals("POST", StringComparison.OrdinalIgnoreCase)) { String input1 = this.Request.Form["Number1"]; String input2 = this.Request.Form["Number2"]; bool error = false; int?number1 = null; int?number2 = null; if (String.IsNullOrEmpty(input1)) { this.ViewBag.Number1Null = "First number is NULL"; error = true; } else { number1 = Convert.ToInt32(input1); } if (String.IsNullOrEmpty(input2)) { this.ViewBag.Number2Null = "Second number is NULL"; error = true; } else { number2 = Convert.ToInt32(input2); } String operation = this.Request.Form["Operation"]; if (number2 == 0 && operation == "/") { this.ViewBag.DividedByZero = "Division by zero"; error = true; } this.ViewBag.Number1 = number1; this.ViewBag.Number2 = number2; this.ViewBag.Operation = operation; if (error) { return(this.View()); } int result = 0; switch (operation) { case "+": result = calculateService.Summ(number1.Value, number2.Value); break; case "-": result = calculateService.Subtraction(number1.Value, number2.Value); break; case "*": result = calculateService.Multiplication(number1.Value, number2.Value); break; case "/": result = calculateService.Division(number1.Value, number2.Value); break; } var resultModel = new CalculateViewModel { ResultNumber = result }; return(this.View("Manual", resultModel)); } return(this.View()); }