string reg = @"(?i)(http://|https://)?(\w+\.){1,3}(com(\.cn)?|cn|net|info|org|us|tk)\b";

            Regex r = new Regex(reg);

            textEditUrl.Text = textEditUrl.Text.Trim();

            Match match = r.Match(textEditUrl.Text);

            if (!match.Success)

            {

                CustomControls.MessageErrDlg dlg = new CustomControls.MessageErrDlg();

                dlg.Text = "Remote Command Failed";

                dlg.ShowDialog();

                textEditUrl.Text = "http://";

            }