It sounds to me like you are developing an ASP.NET Web application that collects the credit card information and then sends it to another site via SSL using an HTTPS POST. If this is the case, you will want your site to run under HTTPS as well, because you don't want clients transmitting credit card information to your site unless it's encrypted. There's no work required for the code-behind code. All the data is encrypted by the browser and decrypted on the Web server before it gets to your code. Now, if your site is the one processing the information, you're ready to go. If you need to forward data to another site for processing and that site is accessed via HTTPS POSTs, then you have some work to do. You'll need to simulate what a browser would do to send the data to the credit card processing site. You can do this using the System.Net.HttpWebRequest class.
This was first published in May 2004