string newPassword = Membership.GeneratePassword(15, 0);
newPassword = Regex.Replace(newPassword, @"[^a-zA-Z0-9]", m => "9" );
This regular expression will replace all non alphanumeric characters with the numeric character 9.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…