Allow 2 decimal points / dots in textbox using c#

Question

I am developing a windows application using c#. 

The user enters a website name which should allow only 2 dots for eg  www.google.com

I have written but that is accepting only 1 dot. The code I have written is :-

if ((e.KeyChar == '.') && ((sender as TextBox).Text.IndexOf('.') > -1))
{
       e.Handled = true;
}

Thanks in Advance ...!!!