Numeric only textbox including scientific notation

[Delaney]

Hello,

EDIT : if you want to have the final version of the custom control, go to the last post.

For one of my application, I had to restrict some textbox entry to numeric only but I accept scientific notation (so 1E5 is ok) and negative value (so the - sign is ok too) and as some of the users have a config that use coma and others that use dot as decimal separator, I dealt also with that. I wanted also that if you type any non valid key, nothing happen (in appearance )

I created 2 functions and worked on the textchanged event.

Function to Check that the text is a number

    Public Function verif_nombre(ByVal text As String) As String
        Dim count As Integer 'To count the number of E
        Dim text_verifie As String = ""
        Dim l As Integer = text.Length
        If l = 0 Then Return text_verifie ' If there is no character, do go further, it is not needed
        Dim charac As Char = text.Chars(text.Length - 1) ' get the last character typed

        If charac = CChar("-") And text.Length = 1 Then ' deal with - sign
            Return text
        End If

        If text.Contains(" ") Then ' replace space by nothing
            text = text.Replace(" ", "")
            Return text
        End If

        'Count the number of e or E in the text
        If text.Contains("e") And text.Contains("E") Then
            count = 2
        ElseIf text.Contains("e") Then
            count = text.Split(CChar("e")).Length - 1
        ElseIf text.Contains("E") Then
            count = text.Split(CChar("E")).Length - 1
        End If

        If count = 1 And (charac = CChar("E") Or charac = CChar("e")) And l > 1 Then 'Deal with the scientific notation
            text_verifie = text
        Else
            If IsNumeric(text) Then ' verify that the text is  numeric
                text_verifie = text
            Else
                text = text.Remove(l - 1) 'if not then remove last charac typed
                text_verifie = text
            End If
        End If
        Return text_verifie
    End Function

Manage dot and coma for the number

Public Function gpv(ByVal text As String) As String 'GPV : gère point-virgule = manage dot - coma ;)
                Dim nfi As NumberFormatInfo = NumberFormatInfo.CurrentInfo 'get the info on the decimal separator for the current user
        If nfi.NumberDecimalSeparator = "." Then 'if dot replace all coma by dot
            text = text.Replace(",", ".")
        Else 'if coma replace dot by coma
            text = text.Replace(".", ",")
        End If
        Return text
    End Function

Method to manage the TextChanged event

Public Sub Numeric_TextBox_TextChanged(sender As Object, e As System.EventArgs)
        Dim TB As TextBox = CType(sender, TextBox)
        TB.Text = verif_nombre(gpv(TB.Text)).ToString
        TB.Select(TB.Text.Length, 0)
    End Sub

On the loading of the forms I handle the event for all textbox based on a tag, if the tag = num then I change the event method

Private Sub Form_Load(sender As Object, e As System.EventArgs) Handles Me.Load
        For Each TB As TextBox In Me.Controls.OfType(Of TextBox)()
            If TB.Tag Is "num" Then
                AddHandler TB.TextChanged, AddressOf Numeric_TextBox_TextChanged
            End If
        Next
    End Sub