Textbox key down event to check for number and letter and decimal

Hello,
I have a function to do a check on keydown event of a textbox ,
how can I have it for only letters,numbers and decimal points

  Public Sub GenericTextBoxFilter(sender As Object, e As KeyEventArgs)
        If TypeOf sender Is RadTextBox Then
            Dim tb = DirectCast(sender, RadTextBox)
            MessageBox.Show(e.KeyValue.ToString())
            If (e.KeyValue.ToString()) = 192 Then
                e.SuppressKeyPress = True
                e.Handled = True
            End If
        End If
    End Sub

Select allOpen in new window