Textbox formatting in VB.net

Question

I want to format my textbox in a way so that, user cant enter any symbol eg () , . ; ' " £ $ % ^[]{}

If (Char.IsDigit(e.KeyChar) Or Char.IsControl(e.KeyChar) Or (e.KeyChar = ".")) Then
             e.Handled = True

End if

This code will prevent user from entering digit or integer. But how can I prevent symbols?

Thanks in advance.

Answer 1

How about

Not Char.IsLetter(e.KeyChar)

?

Answer 2

You can also use a "masked edit" from Ajax. The Ajax control toolkit can be found at:

http://www.asp.net/ajax/ajaxcontroltoolkit/Samples/MaskedEdit/MaskedEdit.aspx

Install Ajax. Follow the steps provided on the websites on how to add the AJAX controls to my Visual Studio. After that, drag the "MaskedEditExtender" Control to the textbox you want formatted.

In the properties field that says "Mask" I typed (999) 999-9999

After this I found out that I had to add something called "TollkitScriptManager" In design view, drag and drop the control above the txtbox which is the textbox you want the formatting done in. I do not think you have to change any of the properties to this and I believe that this control HAS to be above the textbox you want to format.

This may or may not be what you are looking for but it will allow a very specific format for a text box and force the user to only type in numbers or whatever you choose. This is very useful for formatting telephone numbers in the textbox.

Answer 3

I wrote a simple Class to do this in a previous question . Here is the VB.NET version of the code:

Public Class TextBoxFilter
    <Flags()> Public Enum Filters
        None = 0
        Text = 1
        Numbers = 2
        AlphaNumeric = Filters.Text Or Filters.Numbers
        Currency = 4
        All = Filters.Text Or Filters.Numbers Or Filters.Currency
    End Enum

    Dim _keyFilter As Dictionary(Of TextBox, Filters)
    Dim _allowedKeys As Dictionary(Of TextBox, String)
    Dim _invalidKeys As Dictionary(Of TextBox, String)
    Dim _keyEventArgs As Dictionary(Of TextBox, Windows.Forms.KeyEventArgs)

    Private Shared DecimalMark As String = Application.CurrentCulture.NumberFormat.NumberDecimalSeparator
    Private Shared NegativeMark As String = Application.CurrentCulture.NumberFormat.NegativeSign
    Private Shared CurrencySymb As String = Application.CurrentCulture.NumberFormat.CurrencySymbol
    Private Shared CurrencyDecimal As String = Application.CurrentCulture.NumberFormat.CurrencyDecimalSeparator


    Public Sub New()
        _keyFilter = New Dictionary(Of TextBox, Filters)
        _allowedKeys = New Dictionary(Of TextBox, String)
        _invalidKeys = New Dictionary(Of TextBox, String)
        _keyEventArgs = New Dictionary(Of TextBox, KeyEventArgs)
    End Sub

    'set & remove filter'

    Public Sub SetTextBoxFilter(ByVal textBox As TextBox, ByVal filter As Filters)
        SetTextBoxFilter(textBox, filter, AllowedKeys(textBox), InvalidKeys(textBox))
    End Sub

    Public Sub SetTextBoxFilter(ByVal textBox As TextBox, ByVal allowedKeys As String)
        SetTextBoxFilter(textBox, Filter(textBox), allowedKeys, InvalidKeys(textBox))
    End Sub

    Public Sub SetTextBoxFilter(ByVal textBox As TextBox, _
     ByVal allowedKeys As String, ByVal invalidKeys As String)

        SetTextBoxFilter(textBox, Filter(textBox), allowedKeys, invalidKeys)
    End Sub

    Public Sub SetTextBoxFilter(ByVal textBox As TextBox, ByVal filter As Filters, _
     ByVal allowedKeys As String, ByVal invalidKeys As String)

        If Not _keyFilter.ContainsKey(textBox) Then
            'add the textbox and its filter if it does not exist in '
            'the collection of registered textboxes                 '
            _keyFilter.Add(textBox, filter)
            _allowedKeys.Add(textBox, allowedKeys)
            _invalidKeys.Add(textBox, invalidKeys)
            _keyEventArgs.Add(textBox, New System.Windows.Forms.KeyEventArgs(Keys.None))

            'add the event handlers                                 '
            AddHandler textBox.KeyDown, AddressOf KeyDownUp
            AddHandler textBox.KeyUp, AddressOf KeyDownUp
            AddHandler textBox.KeyPress, AddressOf KeyPress
            AddHandler textBox.Validating, AddressOf Validating
            AddHandler textBox.Disposed, AddressOf Disposed

        Else
            'change the filter of the textbox if it exists in       '
            'the collection of registered textboxes                 '
            _keyFilter(textBox) = filter
            _allowedKeys(textBox) = allowedKeys
            _invalidKeys(textBox) = invalidKeys
        End If
    End Sub

    Public Sub RemoveTextBoxFilter(ByVal textBox As TextBox)
        If _keyFilter.ContainsKey(textBox) Then
            _keyFilter.Remove(textBox)
            _allowedKeys.Remove(textBox)
            _invalidKeys.Remove(textBox)
            _keyEventArgs.Remove(textBox)

            RemoveHandler textBox.KeyDown, AddressOf KeyDownUp
            RemoveHandler textBox.KeyUp, AddressOf KeyDownUp
            RemoveHandler textBox.KeyPress, AddressOf KeyPress
            RemoveHandler textBox.Validating, AddressOf Validating
            RemoveHandler textBox.Disposed, AddressOf Disposed
        End If
    End Sub

    Public Function ContainsTextBox(ByVal textBox As TextBox) As Boolean
        Return _keyFilter.ContainsKey(textBox)
    End Function

    'properties'

    Public Property Filter(ByVal textBox As TextBox) As Filters
        Get
            If ContainsTextBox(textBox) Then
                Return _keyFilter.Item(textBox)
            Else
                Return Filters.None
            End If
        End Get
        Set(ByVal value As Filters)
            SetTextBoxFilter(textBox, value)
        End Set
    End Property

    Public Property AllowedKeys(ByVal textBox As TextBox) As String
        Get
            If ContainsTextBox(textBox) Then
                Return _allowedKeys(textBox)
            Else
                Return ""
            End If
        End Get
        Set(ByVal value As String)
            SetTextBoxFilter(textBox, Me.Filter(textBox), value, Me.InvalidKeys(textBox))
        End Set
    End Property

    Public Property InvalidKeys(ByVal textBox As TextBox) As String
        Get
            If ContainsTextBox(textBox) Then
                Return _invalidKeys(textBox)
            Else
                Return ""
            End If
        End Get
        Set(ByVal value As String)
            SetTextBoxFilter(textBox, Me.Filter(textBox), Me.AllowedKeys(textBox), value)
        End Set
    End Property

    'event handlers'

    Private Sub Disposed(ByVal sender As Object, ByVal e As System.EventArgs)
        RemoveTextBoxFilter(DirectCast(sender, TextBox))
    End Sub

    Private Sub KeyDownUp(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs)
        'assign the modifiers'
        _keyEventArgs(DirectCast(sender, TextBox)) = e
    End Sub

    Private Sub KeyPress(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyPressEventArgs)
        'ensure key pressed is in the allowed keys'

        Dim txt = DirectCast(sender, TextBox)
        Dim c = e.KeyChar
        Dim allowKey As Boolean = IsValidChar(txt, c, txt.SelectionStart)


        'check for backspace & Ctrl combinations if the allowKey is still false'
        If allowKey = False Then
            If _keyEventArgs(txt).Control Then
                'control modifier goes with A, X, C, V and Z for '
                'Select All, Cut, Copy, Paste and Undo respectively'
                Dim key = _keyEventArgs(txt).KeyCode
                allowKey = (key = Keys.A OrElse key = Keys.X OrElse _
                   key = Keys.C OrElse key = Keys.V OrElse key = Keys.Z)

            ElseIf _keyEventArgs(txt).KeyCode = Keys.Back Then
                'allow the backspace key'
                allowKey = True
            End If
        End If


        'disable the key if it was not valid'
        If Not allowKey Then
            e.Handled = True
            Beep()
        End If
    End Sub

    Private Sub Validating(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs)
        Dim box = DirectCast(sender, TextBox)
        Dim boxFlags = _keyFilter(box)

        'skip validation if the textbox allows all entries or there is no text'
        If boxFlags = Filters.All Or box.Text = "" Then Exit Sub

        'otherwise check the characters entered'
        Dim txtChars = box.Text.ToCharArray

        Dim isValidEntry As Boolean = False

        'check each caracter for an invalid entry'
        For i = 0 To txtChars.Length - 1
            Dim c = txtChars(i)
            isValidEntry = IsValidChar(box, txtChars(i), i)

            If Not isValidEntry Then
                box.Select(i, 1)
                Exit For
            End If
        Next

        If Not isValidEntry Then e.Cancel = True

        If Not isValidEntry Then
            MsgBox("The text entered is invalid for the format " & boxFlags.ToString & "." & _
             If(_allowedKeys(box) <> "", vbCrLf & "Additional Allowed Keys: " & _allowedKeys(box), "") & _
             If(_invalidKeys(box) <> "", vbCrLf & "Additional Invalid Keys: " & _invalidKeys(box), ""), _
             MsgBoxStyle.Critical, "Invalid Entry")
        End If
    End Sub

    Private Function IsValidChar(ByVal textBox As TextBox, ByVal c As Char, ByVal charIndex As Integer) As Boolean
        'ensure key pressed is in the allowed keys '

        Dim pF = _keyFilter(textBox)
        Dim aK = _allowedKeys(textBox)
        Dim iK = _invalidKeys(textBox)
        Dim shouldAllow As Boolean = False


        'if filter is set to all, return true unconditionally '
        If pF = Filters.All Then Return True


        'check preset filters '

        'check for text '
        If EnumHasFlag(pF, Filters.Text) Then
            If Not Char.IsDigit(c) Then
                shouldAllow = True
            Else
                'if the character is a digit, check for the number flag (AlphaNumerics) '
                If EnumHasFlag(pF, Filters.Numbers) Then
                    shouldAllow = True
                End If
            End If

        End If

        'check for numbers '
        If shouldAllow = False AndAlso EnumHasFlag(pF, Filters.Numbers) Then
            If Char.IsDigit(c) Then
                shouldAllow = True
            ElseIf DecimalMark.Contains(c) Then
                'allow the decimal if there is no decimal in the textbox's
                'text or the selected text contains the mark'
                If Not textBox.Text.Contains(c) OrElse textBox.SelectedText.Contains(c) Then
                    shouldAllow = True
                End If
            ElseIf NegativeMark.Contains(c) AndAlso _
              (charindex <= NegativeMark.IndexOf(c)) Then
                'allow the negative mark if we are at the start of the'
                'textbox'
                shouldAllow = True
            End If

        End If

        'check for currency '
        If shouldAllow = False AndAlso EnumHasFlag(pF, Filters.Currency) Then
            If Char.IsDigit(c) Then
                shouldAllow = True
            ElseIf CurrencyDecimal.Contains(c) Then
                'allow the currency decimal mark if it does not exist in the '
                'textbox''s text or the selected text contains the mark '
                If Not textBox.Text.Substring(0, charIndex).Contains(c) OrElse _
                  textBox.SelectedText.Contains(c) Then
                    shouldAllow = True
                End If
            ElseIf CurrencySymb.Contains(c) AndAlso _
              (charIndex <= CurrencySymb.IndexOf(c)) Then
                'allow the currency symbol if we are in a valid position'
                shouldAllow = True
            End If

        End If



        'now check for extra allowed keys'
        If Not shouldAllow Then
            shouldAllow = aK.Contains(c)
        End If

        'and then check for extra invalid keys'
        If shouldAllow AndAlso iK.Contains(c) Then
            shouldAllow = False
        End If


        Return shouldAllow
    End Function

    <System.Diagnostics.DebuggerStepThrough()> _
     Private Function EnumHasFlag(ByVal value As [Enum], ByVal flag As [Enum]) As Boolean
        Return (Convert.ToInt64(value) And Convert.ToInt64(flag)) = Convert.ToInt64(flag)
    End Function
End Class

Just place this class in your project and use it in your form as follows

Public Class Form1 

    Dim filter = New TextBoxFilter()

    Private Sub Form1_Load(object sender, System.EventArgs e) Handles MyBase.Load
        filter.SetTextBoxFilter(TextBox1, TextBoxFilter.Filters.Numbers)
    End Sub
End Class

Answer 4

U can use use pattern attributes like this

 txtTel.Attributes.Add("placeholder", FormatTel.Libelle)
 txtTel.Attributes.Add("title", FormatTel.Libelle)
 txtTel.Attributes.Add("pattern", FormatTel.ExprReg)

Answer 5

I suggest using regex (regular expressions). What you have to do is checking each and every single character that the user enters. If the characters are invalid you have to replace them with valid characters. The regular expression pattern "[^!@%&$#()*^\\0-9.+-=][_]" matches alphabetic characters and spaces. Symbol ^ in the above pattern means not matching with any of the following characters. Symbol \\ is a scape character and [] denotes a matching range of characters. If the string matches the above pattern you have to replace the character that the user has entered with a valid character.

In the following code, the user input is checked for invalid characters every time he/she enters a new character.

For the code to work you must import the following namespace:

    Imports System.Text.RegularExpressions

The complete code for the windows form is here:

Imports System.Text.RegularExpressions
Public Class RegexTest
    Private Sub TextBox1_TextChanged(sender As Object, e As EventArgs) Handles TextBox1.TextChanged
        Dim theText As String = Me.TextBox1.Text
        Dim cursor1 As Integer = Me.TextBox1.SelectionStart
        Dim cursor2 As Integer = cursor1
        Dim finalText As String = ""
        If theText IsNot Nothing AndAlso theText.Length >= 1 Then
            For x As Integer = 0 To theText.Length - 1 Step +1
                Dim Letter As String = theText.Substring(x, 1)
                Dim extStr As String = ExtractFirstString(Letter, "[^!@%&\$#\(\)\*\^\\0-9\.\+\-=\]\[_]")
                If extStr <> Letter Then
                    extStr = ""
                    finalText &= extStr
                Else
                    finalText &= Letter
                End If
            Next
        End If
        If finalText <> theText Then
            Me.TextBox1.Text = finalText
            Me.TextBox1.SelectionStart = cursor2
        End If
    End Sub


    Private Function ExtractFirstString(ByVal sourceStr As String, ByVal pattern As String) As System.String
        Dim mc As System.Text.RegularExpressions.MatchCollection
        Dim result As String = Nothing
        Dim i As Integer
        Dim brk As Boolean = False
        If sourceStr IsNot Nothing Then
            ' match email addresses!
            mc = Regex.Matches(sourceStr, pattern)
            If mc IsNot Nothing Then
                Dim results(mc.Count - 1) As String
                For i = 0 To results.Length - 1 Step +1
                    result = mc(i).Value
                    brk = True
                    Return result
                    Exit For 'only return the first match
                Next
            End If
        End If
        Return Nothing
    End Function
End Class

You have to create a textbox named TextBox1 on the form and handle its TextChanged evnet.