Imports System.ComponentModel
 
Public Class NumOnlyTextBox
    Inherits TextBox
 
    Private _decimalPositions As Integer
 
    Protected Overrides Sub OnKeyPress(ByVal e As KeyPressEventArgs)
        Dim KeyAscii As Integer
        Dim shDecimalPositions As Short
        Dim shLenDecimals As Short
        Dim X As Short
        Dim decSep As String = _
          System.Threading.Thread.CurrentThread.CurrentCulture.NumberFormat.Cur_
          rencyDecimalSeparator
 
        KeyAscii = Asc(e.KeyChar)
 
        Select Case KeyAscii
            Case 8, 13 'backspace, & carriage return
                'Do nothing to these
            Case 48 To 57 'digits 0-9
                X = InStr(Me.Text, decSep)
                If X > 0 Then
                    X = Me.Text.Length - X + 1
                    If X > DecimalPositions Then
                        KeyAscii = 0
                    End If
                Else
                    Me.Text = FormatNumber(CDec(Me.Text & Chr(KeyAscii)), 0)
                    Me.SelectionStart = Len(Me.Text)
                    KeyAscii = 0
                End If
            Case 45 'minus sign
                'The number can only have one minus sign, so
                'if we already have one, throw this one away
                If InStr(Me.Text, "-") <> 0 Then
                    KeyAscii = 0
                End If
                'if the insertion point is not sitting at zero
                '(which is the beginning of the field), throw away the(minus)
                'sign (because it's not valid except in first position)
                If Me.SelectionStart <> 0 Then
                    KeyAscii = 0
                End If
            Case 46 'This is the period (decimal point)
                'if we already have a period, throw it away, if this key
                'will exceed decimal positions, then throw away.
                If DecimalPositions > 0 Then
                    If InStr(Me.Text, decSep) <> 0 Then
                        KeyAscii = 0
                    End If
                Else
                    KeyAscii = 0
                End If
            Case Else
                'provide no handling for the other keys
                KeyAscii = 0
        End Select
 
        'If we want to throw the keystroke away, then set the event
        'as already handled. Otherwise, let the keystroke be handled normally.
        If KeyAscii = 0 Then
            e.Handled = True
        Else
            e.Handled = False
        End If
 
    End Sub
 
    <DefaultValue("0"), _
     Description("Number of decimal positions"), _
     Category("Behavior")> _
    Public Property DecimalPositions() As Short
        Get
            Return _decimalPositions
        End Get
        Set(ByVal Value As Short)
            _decimalPositions = Value
        End Set
    End Property
 
End Class