Regex pattern UNMATCH in VB.NET or C#

After some thought

Imports System.Text.RegularExpressions
Imports System
Public Class Form1

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
If String.IsNullOrEmpty(TextBox1.Text) Then
Exit Sub
End If
Dim str As String = TextBox1.Text.Trim ' remove whitespaces
checkChar(str)
End Sub


Sub checkChar(ByVal s As String)
Dim _pattern6 As String = "^(7+|8+|9+|6+|5+|4+|3+|2+|1+|(00|07|08|09|17|18|19|28|29|43|48|69|70|78|79|80|96|97).*)$"
Dim m As Match = Regex.Match(s, _pattern6)
If m.Success Then
MessageBox.Show("Invalid characters")
Else
MessageBox.Show("Good to go")
End If

End Sub

Private Sub TextBox1_KeyPress(ByVal sender As System.Object, ByVal e As System.Windows.Forms.KeyPressEventArgs) Handles TextBox1.KeyPress
Dim allowedChars As String = "0123456789" 'numbers only allowed in textbox

If allowedChars.IndexOf(e.KeyChar) = -1 Then
' Invalid Character
e.Handled = True
End If
'In KeyPress event

End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
TextBox1.Text = String.Empty
TextBox1.Focus()
End Sub
End Class

Not sure what you need
 To check 9 characters use

 Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim str As String = TextBox1.Text.Trim ' remove whitespaces
Dim i As Integer = str.Length
If i > 9 Then ' if text longer than 9 chars
MessageBox.Show("Too many characters")
End If
End Sub

Do you want a numbers only textbox ?
The first character cannot be zero ?