How to filter textbox input to numeric only?

Question

How do I suppress all data except numeric?

This is not working on KeyDown():

If e.KeyData < Keys.D0 Or e.KeyData > Keys.D9 Then
          


        

Answer 1

Will help you...

    Public Function IsNumericTextbox(ByVal sender As TextBox, ByVal KeyChar As Char) As Boolean
    'set TRUE: cause a exception when the keychar is not Allowed into vars: allowedChars, allowedOneChar, allowedExceptionChar
    Dim UseThrowDebuggy As Boolean = False

    Dim allowedChars As String = "0123456789"
    Dim allowedOnceChar As Char() = {"."}
    Dim allowedExceptionChar As Keys() = {Keys.Back}

    Dim idxAllowedNotFound As Integer
    Dim idxCountOne As Integer = 0

    idxAllowedNotFound = allowedChars.IndexOf(KeyChar)
    If idxAllowedNotFound = True Then
        'AllowedOnce
        For Each _c As Char In allowedOnceChar
            If _c = KeyChar Then
                'Count Check
                For Each _cc As Char In sender.Text
                    If _c = _cc Then idxCountOne += 1
                Next
                If idxCountOne = 0 Then
                    Return False
                Else
                    Return True
                End If
            End If
        Next
        'Exceptions
        For i As Integer = 0 To allowedExceptionChar.Count - 1
            If Asc(KeyChar) = Convert.ToUInt32(allowedExceptionChar(i)) Then Return False
        Next
        'Not Throw
        If UseThrowDebuggy = False Then
            If Char.IsNumber(KeyChar) Then
                Return False
            Else
                Return True
            End If
        End If
        'Outside to end for throw
    Else
        'AllowedChars
        Return False
    End If

    Dim _kc As String = ControlChars.NewLine & "Char: " & KeyChar & ControlChars.NewLine & "Asc: " & Asc(KeyChar) & ControlChars.NewLine
    Throw New Exception("UseThrowDebuggy found a unknow KeyChar: " & _kc)
End Function

For use my function add this code into a textbox_keypress:

e.Handled = IsNumericTextbox(sender, e.KeyChar)

Answer 2

This will allow numeric input ,Backspace to correct your input , and also a decimal point.

    If (e.KeyChar < "0" OrElse e.KeyChar > "9") AndAlso e.KeyChar <> ControlChars.Back AndAlso e.KeyChar <> ControlChars.Cr AndAlso e.KeyChar <> "." Then
        Beep()
        e.Handled = True
    End If

Answer 3

The purpose of your function could help provide additional solutions. Checking for a numeric value on each KeyPress is likely overkill. Then you have to overkill it more by accounting for backspace, delete, copy, paste, etc.

For example, if you are storing a telephone number, you should use the "IsNumeric" function on the validate and update step. Alternatively, if you are selecting quantity of an item "NumericUpDown" control would be more appropriate than a TextBox.