Y'herd thisun? 

“Millions of Chinese peasants died of famine during the Mao Zedong Great Leap Forward period as agricultural crops proved stubbornly unresponsive to demonstrations of mass enthusiasm. Chinese industrial production also declined as factory machinery proved similarly unresponsive. What worked was Deng Xiaoping's restoration of material incentives for good management and disciplined work”

from Reopening the Space Frontier by John Hickman

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TaggedCoding, VB, Imaging

Originally published December 2002 on using VB7.0/2002. Updated for VB7.1 February 2005

Links for compiled demo versions, all required resources and source code are included at the end of this article.

Plus, get the complete eBook in Adobe Acrobat 7 format ... all here.


26) An integer-only textbox

Add a new usercontrol to your app project, name the file "svIntegerTextbox.vb" and save the file. When the designer is shown, right click to switch to codeview and replace all of the stock code with the following:


Public Class svIntegerTextbox
Inherits System.Windows.Forms.TextBox
#Region " Windows Form Designer generated code "
Public Sub New()
'This call is required by the Windows Form Designer.
'Add any initialization after the InitializeComponent() call
End Sub
'UserControl overrides dispose to clean up the component list.
Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
If disposing Then
 If Not (components Is Nothing) Then
 End If
End If
End Sub
'Required by the Windows Form Designer
Private components As System.ComponentModel.IContainer
'NOTE: The following procedure is required by the Windows Form Designer
'It can be modified using the Windows Form Designer.
'Do not modify it using the code editor.
<system.diagnostics.debuggerstepthrough> Private Sub InitializeComponent()
components = New System.ComponentModel.Container
End Sub
#End Region
#Region "Declarations"
Private m_MinValue As Integer = 0
Private m_MaxValue As Integer = Integer.MaxValue
Private m_DefaultValue As Integer = 0
#End Region
#Region "Public properties"
Public Property DefaultValue() As Integer
 Return m_DefaultValue
End Get
Set(ByVal Value As Integer)
 If Value < m_MinValue OrElse Value > m_MaxValue Then
 m_DefaultValue = (m_MaxValue - m_MinValue) \ 2
 m_DefaultValue = Value
 End If
End Set
End Property
Public Overrides Property MaxLength() As Integer
 Return MyBase.MaxLength()
End Get
Set(ByVal Value As Integer)
 If Value > m_MaxValue.ToString.Length + 1 Then
 Value = m_MaxValue.ToString.Length + 1
 ElseIf Value < m_MaxValue.ToString.Length + 1 Then
 Value = m_MaxValue.ToString.Length + 1
 End If
 Catch ex As Exception
 End Try
 MyBase.MaxLength = Value
End Set
End Property
Public Property MinValue() As Integer
 Return m_MinValue
End Get
Set(ByVal Value As Integer)
 If Not Value > m_MaxValue Then
 m_MinValue = Value
 If m_DefaultValue < m_MinValue Then
 m_DefaultValue = m_MinValue
 End If
 If CInt(Me.Text) < m_MinValue Then
 'force a fix
 Me.Text = FixEntry(Me.Text)
 End If
 End If
End Set
End Property
Public Property MaxValue() As Integer
 Return m_MaxValue
End Get
Set(ByVal Value As Integer)
 If Not Value < m_MinValue Then
 m_MaxValue = Value
 MyBase.MaxLength = m_MaxValue.ToString.Length + 1
 'security against changing maxlength/maxval after
 'after a larger value has been entered in the textbox
 If m_DefaultValue > m_MaxValue Then
 m_DefaultValue = m_MaxValue
 End If
 If CInt(Me.Text) > m_MaxValue Then
 'force a fix
 Me.Text = FixEntry(Me.Text)
 End If
 End If
End Set
End Property
#End Region
#Region "Private methods"
Private Function FixEntry(ByVal Value As String) As String
Dim s As String = Value.Trim.Replace(" ", "")
Dim sVal As Long
Dim arc() As Char = s.ToCharArray
s = ""
For i As Integer = 0 To arc.GetUpperBound(0)
 If IsNumeric(arc(i)) Then
 s &= arc(i)
 End If
If s.Length = 0 Then
 Return m_DefaultValue.ToString
 sVal = CLng(s)
 If sVal > CLng(m_MaxValue) Then
 Return m_MaxValue.ToString
 ElseIf sVal < CLng(m_MinValue) Then
 Return m_MinValue.ToString()
 Return CInt(sVal).ToString
 End If
End If
End Function
#End Region
#Region "Base methods"
Protected Overrides Sub OnLayout(ByVal levent As System.Windows.Forms.LayoutEventArgs)
'called in the IDE at designtime
Me.Text = m_DefaultValue.ToString
Me.MaxLength = m_MaxValue.ToString.Length + 1
End Sub
Protected Overrides Sub OnTextChanged(ByVal e As System.EventArgs)
Static bFixing As Boolean
If bFixing Then Exit Sub
bFixing = True
Dim iCurPos As Integer = Me.SelectionStart
Dim sOrig As String = Me.Text
Dim sFixed As String = FixEntry(sOrig)
If sOrig <> sFixed Then
 Me.Text = sFixed
End If
If Me.Text = "0" Then
ElseIf iCurPos > 0 Then
 Me.SelectionStart = iCurPos
End If
bFixing = False
End Sub
Private Sub IntegerTextbox_LostFocus(ByVal sender As Object, _
 ByVal e As System.EventArgs) Handles MyBase.LostFocus
If Me.Text = "" Then Me.Text = FixEntry(Me.Text)
End Sub
#End Region
End Class

Most of the work is done in the FixEntry function, where the text is analyzed character by character and compared against the min and max properties. The one little neat routine is the OnLayout event handler which sets the text when the dev-user drops an instance on a form at designtime; you have to force the text in this event because the base textbox default is the name of the instance plus an incremented counter and if you don't deal with it then each instance will be automatically set to the trimmed instance number which can be a bit confusing.

Rebuild the project so the usercontrol is usable then drop instances on the form as shown in the previous sample graphic,naming each to fit the specific usages.

One last thing on the save options form, the 'Aspect Correct By Max' needs a checkbox to specify whether the value is for the width or height. Add that defaulting to checked so the width will be used.

Next: Passing save options between forms

Robert Smith
Kirkland, WA

added to smithvoice march 2005


jump to:

  • 1) The spec
  • 2) Setting up the workspace
  • 3) Feature 1: Loading an image
  • 4) Custom Exceptions
  • 5) "Fax images" and Multipage TIFFs
  • 6) Custom events
  • 7) Selecting specific fax pages
  • 8) Feature 2: Rotating image displays
  • 9) The most useful tool in GDI+: DrawImage
  • 10) Feature 3: Zooming
  • 11) Handling the unhandleable exception
  • 12) Fixing the squish
  • 13) Zooming to fit the control
  • 14) You're already beating the Pros
  • 15) Feature 4: Cropping
  • 16) Bonus Feature: StickyMouse
  • 17a) Final Cleanup
  • 17b) Passing the current display image
  • 18) Making the application
  • 19) Source and result viewports
  • 20) A better toolbar
  • 21) Hooking the toolbar to the project
  • 22) Adding ImageEditors
  • 23) The toolbar ZoomCombo
  • 24) The final solution
  • 25) Saving to image files
  • 26) An integer-only textbox
  • 27) Passing save options between forms
  • 28) Dealing with that last exception
  • 29) Offer more options with menus
  • 30 The downloads and ebook

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