Console Application on VB2008 - Integer.TryParse Method Error - vb.net

Question

I am using Integer.TryParse Method to validate whether user input is a numeric or non-numeric in my program.
1)if the user input is numeric, the program will then proceed and validate that the user input is range from 0 to 9.
2)If the user is enter a non-numeric input, the program will display the message "invalid input" and ask user to start from beginning.
Following is my coding:
Sub Main()
Dim sevenNumbers As Integer()
sevenNumbers = New Integer(6) {}
Dim index As Integer
Dim number As Integer
Dim reEnter As Boolean = True
Console.WriteLine("Please enter 7 integers: ")
Console.WriteLine("<ATTENTION: FROM 0 TO 9 ONLY>")
Console.WriteLine()
While reEnter
For index = 0 To 6
Console.WriteLine("Please enter the integer no." & "{0}" & " : ", index + 1) 'Prompt user to enter 7 integers.
sevenNumbers(index) = Console.ReadLine() 'The 7 integers are stored in an array.
If Integer.TryParse(sevenNumbers(index), number) Then
While sevenNumbers(index) < 0 Or sevenNumbers(index) > 9
Console.WriteLine("<invalid input>")
Console.WriteLine()
Console.WriteLine("------------------------------------------")
Console.WriteLine("<Please re-enter the 7 integers>")
Console.WriteLine("------------------------------------------")
Console.WriteLine()
reEnter = True
Exit For
End While
Else
Console.WriteLine("<invalid input>")
Console.WriteLine()
Console.WriteLine("------------------------------------------")
Console.WriteLine("<Please re-enter the 7 integers>")
Console.WriteLine("------------------------------------------")
Console.WriteLine()
reEnter = True
Exit For
End If
reEnter = False
Next
End While
End Sub
However, when a user enter a non-numeric input, the program can't continue and shows an error that forced to close.
i tried this
Sub Main()
Dim num As Integer
Console.Write("enter num:")
Dim input = Console.ReadLine
If Integer.TryParse(input, num) Then
Console.WriteLine("valid. num = " & num)
Else
Console.WriteLine("invalid")
End If
End Sub
it does works and i am wondering which part of my coding is wrong??
Thank for help!!

Answer 1

Your two samples of code are different. In your second attempt, you do this:
Dim input = Console.ReadLine
If Integer.TryParse(input, num) Then
The above code reads into a variable called input that will be a String (because Console.ReadLine returns a String). Then, you try to parse the string into a number.
However, in your original code, you do this (some lines omitted for clarity):
Dim sevenNumbers As Integer()
sevenNumbers = New Integer(6) {}
...
sevenNumbers(index) = Console.ReadLine()
In this case, you are reading into a variable that you have explicitly declared to be an Integer. If the user types "abc" then the conversion will fail at this point - you won't even get to the TryParse because you can't complete the innput.
Instead of reading to an integer, you need to read into a String variable and then parse that value into an Integer (as you did in your second code).
You could have spotted this yourself by taking note of the line that the error actually occurs on when debugging: you should note that the program crashes on the ReadLine, not on the TryParse.

Answer 2

Um. This line:
sevenNumbers(index) = Console.ReadLine()
Is storing whatever text has been read into an array of Integers. If it's compiling, then by the time you reach any later code, you're too late to control the conversion. It's already happened.
Maybe sevenNumbers should be String()?
(You really ought to turn on OPTION STRICT and OPTION EXPLICIT - it should find problems like this for you when it compiles the code)