Patrick McKenzie recently wrote a really good article on just this topic. Highly recommended. http://www.kalzumeus.com/2012/01/23/salary-negotiation/[^]

For generating thumbnails, take a look at the GetThumbnailImage method of the Image class. It's perfect for this — I've used it for just this purpose in the past (displaying small images to save bandwidth and load time on an ASP.NET site). I can't help you with displaying them though, as you don't show any markup or your Page_Load method and the like. Remember, though, that if you are generating thumbnails on the fly in memory on the server, these do not exist anywhere on disk. When the HTML is loaded in the client browser, the img element needs an src URL. This is, as you probably know, typically a direct link to a .jpg somewhere on your webserver virtual directory or something. Usually it is a disk file. Since these are not really saved, you can't link to a file. But you have to link to something! What we did is create an aspx page that returns image data (not html). You can find a good guide to this here (which also shows using the GetThumbnailImage method I mentioned before). You then will basically use an Image control and set its ImageUrl to MakeThumbnail.aspx?file=picture.jpg or the like. In our case, we had images stored in a database, so we used an integer id instead of a file name.