working with Arrays, runtime error

Question

Hello, I am getting an error with the code below. I am trying to enter the number from a txtBox into an array intPin(0), but the error tells me that intPin was nothing. Please advise.

Public Class Form1
Dim intMinPin() As Integer = {7, 5, 0, 0, 6, 3, 4}
Dim intMaxPin() As Integer = {9, 7, 4, 9, 9, 6, 8}
Dim intCount As Integer
Dim val As Integer
Dim intPin() As Integer

' Dim intSeries(intMAX_SUBSCRIPT) As Integer

Private Function ValidateInputFields() As Boolean
    If Not Integer.TryParse(TextBox1.Text, intPin(0)) Then
        MessageBox.Show("Enter numeric digit in textbox1")
        Return False
    ElseIf intPin(0) <= intMinPin(0) >= intMaxPin(0) Then
        Return False
        MessageBox.Show("enter a number between 7 & 9 in Text Box1")
    Else
        Return True
    End If

End Function

Answer 1

Change:
Const intMAX_SUBSCRIPT As Integer = 7
to:
Const intMAX_SUBSCRIPT As Integer = 6

Since arrays are zero based.
Also move Const intMAX_SUBSCRIPT As Integer = 6, above intPin

Answer 2

The following is conceptual

• May be too much for you (many coders say I want simple while simple is dependent on how one sees the big picture)
• May not fit your needs as shown but once understood should provide a base for what you are after
• You may need to adjust a few things.
• The custom TextBox could be used in other projects. It only accepts numbers, disallows paste from clipboard. Can be customer farther. Can lose the PIN part for other projects.

A custom TextBox is use, Index property indicates pin order in this case, MinAcceptableValue and MaxAcceptableValue properties indicate what the range can be for the TextBox. GetRange (may need a better name) is used for failed validation in PinValidator.Validate.

PinRange checks in values are in range using a generic extension method

Custom Numeric validator TextBox

Imports System.ComponentModel  
  
Namespace Helpers  
  
    Public Class NumericTextbox  
        Inherits TextBox  
  
        Public Sub New()  
            TextAlign = HorizontalAlignment.Right  
        End Sub  
  
        <Description("PIN Index"), Category("Behavior")>  
        Public Property Index() As Integer  
        ''' <summary>  
        ''' Is PIN in a valid range  
        ''' </summary>  
        ''' <returns></returns>  
        Public ReadOnly Property PinInRange() As Boolean  
            Get  
                Return Pin.Between(MinAcceptableValue, MaxAcceptableValue)  
            End Get  
        End Property  
  
        <Description("Min value"), Category("Range")>  
        Public Property MinAcceptableValue() As Integer  
  
        <Description("Max value"), Category("Range")>  
        Public Property MaxAcceptableValue() As Integer  
        ''' <summary>  
        ''' Get range message  
        ''' </summary>  
        ''' <returns></returns>  
        Public ReadOnly Property GetRange() As String  
            Get  
                Return $"PIN{Index} range {MinAcceptableValue} and {MaxAcceptableValue}"  
            End Get  
        End Property  
  
        Const WM_PASTE As Integer = &H302  
        ''' <summary>  
        ''' PIN value  
        ''' </summary>  
        ''' <returns></returns>  
        <Browsable(False)>  
        Public ReadOnly Property Pin As Integer  
            Get  
                If String.IsNullOrWhiteSpace(Text) Then  
                    Return 0  
                Else  
                    Return CInt(Text)  
                End If  
            End Get  
        End Property  
#Region "OnKeyPress and WndProc"  
  
        Protected Overrides Sub OnKeyPress(ByVal e As KeyPressEventArgs)  
            Dim value As String = Text  
            value = value.Remove(SelectionStart, SelectionLength)  
            value = value.Insert(SelectionStart, e.KeyChar)  
  
            e.Handled = value.LastIndexOf("-", StringComparison.Ordinal) > 0 _  
            Or Not (Char.IsControl(e.KeyChar) OrElse  
                        Char.IsDigit(e.KeyChar) OrElse  
                    (e.KeyChar = "."c And Not Text.Contains(".") Or e.KeyChar = "."c And MyBase.SelectedText.Contains(".")) OrElse  
                    (e.KeyChar = "-"c And SelectionStart = 0))  
  
            MyBase.OnKeyPress(e)  
  
        End Sub  
        Protected Overrides Sub WndProc(ByRef m As Message)  
  
            If m.Msg = WM_PASTE Then  
  
                Dim value As String = Text  
  
                value = value.Remove(SelectionStart, SelectionLength)  
                value = value.Insert(SelectionStart, Clipboard.GetText)  
  
                Dim result As Decimal = 0  
                If Not Decimal.TryParse(value, result) Then  
                    Return  
                End If  
  
            End If  
  
            MyBase.WndProc(m)  
  
        End Sub  
  
#End Region  
    End Class  
End Namespace  

Generic extensions (works on numbers and dates)

Imports System.Runtime.CompilerServices  
  
Namespace Helpers  
  
    Public Module GenericExtensions  
        <Extension>  
        Public Function Between(Of T)(sender As IComparable(Of T), minimumValue As T, maximumValue As T) As Boolean  
            Return sender.CompareTo(minimumValue) >= 0 AndAlso sender.CompareTo(maximumValue) <= 0  
        End Function  
    End Module  
End Namespace  

Validator for a button click

Namespace Helpers  
    Public Class PinValidator  
        Public Shared Function Validate(sender As List(Of NumericTextbox)) As String  
            Return If(sender.Any(Function(box) box.PinInRange = False),  
                      "Invalid values" & Environment.NewLine & String.Join(Environment.NewLine,  
                                  sender.Where(Function(item) item.PinInRange = False).  
                                Select(Function(x) x.GetRange).ToArray()),  
                      "Accepted")  
        End Function  
    End Class  
End Namespace  

Form code

Imports PinValidate.Helpers  
  
Public Class Form1  
    Public PinBoxes As List(Of NumericTextbox)  
  
    Private Sub ValidateButton_Click(sender As Object, e As EventArgs) Handles ValidateButton.Click  
        MessageBox.Show(PinValidator.Validate(PinBoxes))  
    End Sub  
  
    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load  
        PinBoxes = Controls.OfType(Of NumericTextbox).OrderBy(Function(box) box.Index).ToList()  
    End Sub  
End Class  

At design time some properties (I changed category from above to fit custom properties onto a small screenshot)

By Hand

Pin1Textbox.Text = "2"  
Pin1Textbox.MinAcceptableValue = 1  
Pin1Textbox.MaxAcceptableValue = 3  
Console.WriteLine(Pin1Textbox.PinInRange)  
  
Pin1Textbox.Text = "20"  
Console.WriteLine(Pin1Textbox.PinInRange)  

---

Answer 3

Hi @Hekzdaddy ,
In order to make textbox accept only numbers, you can also take a look at the following code:

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load  
        AddHandler TextBox1.KeyPress, AddressOf TextBox_KeyPress  
        AddHandler TextBox2.KeyPress, AddressOf TextBox_KeyPress  
        '...  
    End Sub  
    Private Sub TextBox_KeyPress(ByVal sender As Object, ByVal e As KeyPressEventArgs)  
        If Not Char.IsControl(e.KeyChar) AndAlso Not Char.IsDigit(e.KeyChar) AndAlso (e.KeyChar <> "."c) Then  
            MessageBox.Show("Enter numeric digit in textbox")  
            e.Handled = True  
        End If  
  
        If (e.KeyChar = "."c) AndAlso ((TryCast(sender, TextBox)).Text.IndexOf("."c) > -1) Then  
            MessageBox.Show("Only allow one decimal point")  
            e.Handled = True  
        End If  
    End Sub  

Hope it could be helpful.

Best Regards,
Xingyu Zhao
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