How do I fix this exception handling

Question

1.00/5 (1 vote)

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I need this to validate an input from the user. It needs to ensure that it is numeric and that it is in the range of -1 - 5 including 0 as a valid input.

What I have tried:

Sub Main()
       Dim Years As Integer
       Dim Valid As Boolean = False

       Do Until Valid = True
           Console.WriteLine("Enter a number between -1 and  5")

           If IsNumeric(Console.ReadLine) Then
               Years = Console.ReadLine()
               Console.WriteLine()
               Select Case Years
                   Case -1 To 5
                       Valid = True
                   Case Else
                       Console.WriteLine("The number is outside the range")

               End Select
               Console.WriteLine("Enter a valid number")
           End If


       Loop
       Console.ReadLine()
   End Sub

Posted 18-Oct-17 1:37am

Teal_

Updated 18-Oct-17 4:41am

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Comments

Richard MacCutchan 18-Oct-17 7:49am

What is the question?

Teal_ 18-Oct-17 7:56am

currently the code posted will catch if a alpha numeric is entered but if a number outside or inside the range is entered it will throw the error on the line "Years = Console.Readline" "Conversion from string "" to type 'Integer' is not valid". I don't know why this is happening. Additionally when i remove the "if IsNumeric(console.readline) Then " it works. I would like help fixing it so that it will only exit the loop if a number between -1 and 5 is entered

ZurdoDev 18-Oct-17 8:03am

Console.ReadLine take input from the user. So, don't call it twice. Store it in a string and then check it.

"Conversion from string "" to type 'Integer' is not valid". - Look at your code. You defined Years as an Integer so when you type in something that is not integer, you'll get that error.

Peter_in_2780 18-Oct-17 8:00am

Your problem is calling Console.ReadLine twice. You need to call it once, and use that result to test then convert.

2 solutions

Solution 1

Because you are trying to read the input twice. Your code should be something like this:

VB

Try
    Years = Console.ReadLine()
    Console.WriteLine()
    ' check for valid number etc. ...

Catch Exception ' of some type
    Console.WriteLine("Enter a valid number")
End Try

Posted 18-Oct-17 2:04am

Richard MacCutchan

Comments

Ralf Meier 18-Oct-17 9:13am

Years is defined as integer.
Console.Readline will bring you a string - so I suggest to make a converting of this to Integer ...

Richard MacCutchan 18-Oct-17 10:53am

Thank you. I should have seen that, but I am very much a novice at VB.NET.

Ralf Meier 19-Oct-17 2:12am

I don't believe you ... ;) ... but no matter ... :)

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Bryian Tan · Accepted Answer · 2017-10-18T04:19:00

You can use Int32.TryParse function and a minor tweak to get the desire result. See below.

VB

Dim Years As Integer
        Dim Valid As Boolean = False

        Console.WriteLine("Enter a number between -1 and  5")

        Do Until Valid = True
            If (Int32.TryParse(Console.ReadLine(), Years)) Then
                Select Case Years
                    Case -1 To 5
                        Valid = True
                        Console.WriteLine("Good job!!!")
                    Case Else
                        Console.WriteLine("The number is outside the range")
                End Select
            Else
                Console.WriteLine("Enter a valid number")
            End If

        Loop
        Console.ReadLine()

Here the link to test it out VB Console Integer Range[^]