Discussion – Lesson 7 - Sanitizing user input in VB.NET

Hi,
I've tried to make some changes in the last code of the lesson 7. Please, could check it? Thanks!

Module Module1

    Sub Main()

        Dim goOn As String = "yes"
        While goOn = "yes"
            ' reading numbers
            Console.WriteLine("Enter the first number:")
            Dim a As Double
            While Not Double.TryParse(Console.ReadLine(), a)
                Console.WriteLine("Invalid entry, please try again:")
            End While
            Console.WriteLine("Enter the second number:")
            Dim b As Double
            While Not Double.TryParse(Console.ReadLine(), b)
                Console.WriteLine("Invalid entry, please try again:")
            End While
            ' operation choice and calculation
            Console.WriteLine("Choose one of the following operations:")
            Console.WriteLine("1 - addition")
            Console.WriteLine("2 - subtraction")
            Console.WriteLine("3 - multiplication")
            Console.WriteLine("4 - division")
            Dim choice As Char = Console.ReadKey().KeyChar
            Console.WriteLine()

            Dim result As Double = 0
            Dim validChoice As Boolean = True
            Select Case choice

                Case "1"
                    result = a + b
                Case "2"
                    result = a - b
                Case "3"
                    result = a * b
                Case "4"
                    result = a / b
                Case Else

                    validChoice = False
            End Select
            If validChoice Then
                Console.WriteLine("Result: {0}", result)
            Else
                Console.WriteLine("Invalid choice")
            End If
            Console.WriteLine("Would you like to make another calculation? [yes/no]")
            ' request to continue
            validChoice = False

            While Not validChoice
                Select Case Console.ReadKey().KeyChar.ToString().ToLower()


                    Case "y"
                        goOn = "yes"
                        validChoice = True
                        Console.WriteLine()
                    Case "n"
                        goOn = "no"
                        validChoice = True
                        Console.WriteLine()
                    Case Else

                        Console.WriteLine("Invalid option, please enter yes/no")
                End Select
            End While
        End While
        Console.WriteLine("Thank you for using our calculator. Press any key to end the program.")
        Console.ReadKey()
    End Sub
End Module

Seems fine to me, good job

Hi David, there is an error in your code, if you enter 'y' it's just continuing the loop with the same statement, please have a look at the attached image.
Cheers.

Thanks for pointing that out! There's been a typo in the code. There should be Case "y" instead of Case "a". Please fix that in your code and it should work then

Still, there is a problem in that code, but if you change the values to "yes" and "no" it's working fine.
Select Case Console.ReadKe­y().KeyChar.ToS­tring().ToLower()
Case "y"
goOn = True
validChoice = True
Case "n"
goOn = False
validChoice = True

Working Code

Select Case Console.ReadKe­y().KeyChar.ToS­tring().ToLower()
Case "y"
goOn = "yes"
validChoice = True
Case "n"
goOn = "no"
validChoice = True
Please have a look at the image.
Thank you
was

A modified version of your code, everything works perfectly. Thank you

Dim goOn As Boolean = True
       Dim crlf As String = Chr(13) + Chr(10)
       While goOn
           'reading numbers
           Console.WriteLine(crlf + "Welcome to our calculator!")
           Console.WriteLine("==========================")
           Console.WriteLine(crlf + "Enter the first number:")
           Dim a As Double
           While Not Double.TryParse(Console.ReadLine(), a)
               Console.WriteLine(crlf + "Invalid entry, try again:")

           End While
           Console.WriteLine(crlf + "Enter the second number:")
           Dim b As Double
           While Not Double.TryParse(Console.ReadLine(), b)
               Console.WriteLine(crlf + "Invalid entry, try again:")
           End While

           'operation choice and calculation
           Console.WriteLine(crlf + "Choose one of the following operations:")
           Console.WriteLine("1- Addition:")
           Console.WriteLine("2- Subtraction:")
           Console.WriteLine("3- Multiplication:")
           Console.WriteLine("4- Division:")
           Dim choice As Char = Console.ReadKey().KeyChar
           Dim result As Double = 0
           Dim validChoice As Boolean = True
           Select Case choice
               Case "1"
                   result = a + b
               Case "2"
                   result = a - b
               Case "3"
                   result = a * b
               Case "4"
                   result = a / b
               Case Else
                   validChoice = False
           End Select
           If validChoice Then
               Console.WriteLine(crlf + "Result: {0}", result)
           Else
               Console.WriteLine("Invalid choice")
           End If
           Console.WriteLine(crlf + "Would you like to make another calculation? [yes/no]")
           'request to continue
           validChoice = False
           While Not validChoice
               Select Case Console.ReadKey().KeyChar.ToString().ToLower()
                   Case "y"
                       goOn = True
                       validChoice = True
                   Case "n"
                       goOn = False
                       validChoice = True
                   Case Else
                       Console.WriteLine(crlf + "Invalid option, please enter y/n")



               End Select
           End While

       End While
       Console.WriteLine("Thank you for using our calculator. Press any key to end the program.")
       Console.ReadKey()