Simple example of validating a phone number:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
     
' Invalid phone number
     'Dim strPhone As String = "123456789"

    ' valid phone number
    Dim strPhone As String = "(123) 456-7890"
    Dim regexp As New Regex(("^\(?\d{3}\)?\s|-\d{3}-\d{4}$"))

     If
regexp.IsMatch(strPhone) Then
           MsgBox("Valid Phone Number")
    Else
          MsgBox("Invalid Phone Number")
   End If

End
Sub