You don't generate emoticon. They are simply image file, which can be jpg, gif or what ever other format you like. Don't try to generate, but you will need to reference them.
1. You need the set of images you will need to work with
2. Designate some tags to be used as place holders in your content (usually this is user supplied data)
3. Parse your input and substitute your tags for real images.
4. Look, you got some shiny emoticons displayed. Wow!
May be this can give you some hint.
http://www.davidpirek.com/blog.aspx?n=Emoticons-in-ASP.NET:-how-to-generate-Emoticons[
^]