Visual Basic: Loop & Array

[grant_cpt]

Hi there

Been busy practicing for my practical programming exam. And I've been bumping into this specific bug.



Please have a look at my code, and tell me if you spot anything wrong.

Regards
Grant

Public Class Form1

Dim strProvinces(8) As String
    Dim i As Integer = 0

Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click
        Dim blnFlag As Boolean = False


Do While blnFlag = False
            If String.IsNullOrEmpty(Me.txtInput.Text) Then
                blnFlag = True
                MsgBox("Empty")
                Me.txtInput.Focus()
                Exit Do
            Else
                If Me.txtInput.Text = strProvinces(i) Then
                    blnFlag = True
                    MsgBox("Duplicate Found")
                    Me.txtInput.Clear()
                    Me.txtInput.Focus()
                    Exit Do
                Else
                    If i >= 9 Then
                        blnFlag = True
                        MsgBox("There is only 9")
                        Me.txtInput.Clear()
                        Exit Do
                    End If
                End If
            End If

            strProvinces(i) = Me.txtInput.Text
            lsbDisplay.Items.Add(strProvinces(i))
            i = i + 1
        Loop
        Exit Sub
End Sub

 

[cguy]

The last version of BASIC I've used was GW BASIC, but it looks as though you are checking for i >= 9 after you've accessed strProvinces(9), which is why you are getting the out of bounds exception. Assuming these array indices are 1 based (it's been awhile), you probably just have do the i >= 9 check before the "Me... = strProvinces(i)" check.

 

[scudsucker]

Change

Else
If i >= 9 Then

to

Else
If i > 9 Then

And then change your language to C#. VB is pretty horrible.

 

[tridev]

You get the error because your array has only 8 places so when you refer to position 9 with strProvinces(9) you get an exception as that position doesn't exist in the array.
To fix either change to

Dim strProvinces(9) As String

or

 If i >= 8 Then

or move the whole if check block to before you reference the array

 Private Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click

        Dim blnFlag As Boolean = False


        Do While blnFlag = False
            If i >= 9 Then
                blnFlag = True
                MsgBox("There is only 9")
                Me.txtInput.Clear()
                Exit Do

            Else
                If String.IsNullOrEmpty(Me.txtInput.Text) Then
                    blnFlag = True
                    MsgBox("Empty")
                    Me.txtInput.Focus()
                    Exit Do
                Else
                    If Me.txtInput.Text = strProvinces(i) Then
                        blnFlag = True
                        MsgBox("Duplicate Found")
                        Me.txtInput.Clear()
                        Me.txtInput.Focus()
                        Exit Do

                    End If
                End If
            End If

            strProvinces(i) = Me.txtInput.Text
            lsbDisplay.Items.Add(strProvinces(i))
            i = i + 1
        Loop
        Exit Sub
    End Sub

 

[scudsucker]

oh.. and for the love of god please don't use "Me" to reference current scope.

And while I'm being a dick, please try to avoid flags:

blnFlag = False

And hungarian notation. .NET is type-safe; you don't need the hint.

blnFlag

... and finally, please assure me this is a .exe, not a website. Because, if it is a website, please.. PLEASE look into ASP.NET MVC.


(disclaimer: I am a dick in general but I do not mean to be a dick to you specifically. You seem like a beginner so my advice is given honestly)

 

[tridev]

He is at school. Don't be hard on him

 

[tridev]

VB is funny If you have an array of 9 provinces you can specify it like this strProvinces(8) and will allow you to reference strProvince(0) to strProvinces[8] e.g. 9 items

but in C# the correct way string [] strProvinces= new string[8] you can only reference position 0 to 7

So if he converted the working code from VB into C# it would throw an exception

 

[Hamish McPanji]

(disclaimer: I am a dick in general but I do not mean to be a dick to you specifically. You seem like a beginner so my advice is given honestly)

Quoted for reference