It is really amazing what free external services can do bring additional functionality to your web application. During the hackathon I got the chance to add three services to app that really made it feel whole.
I first learned about Gravatar when I found it being used on the MemphisJUG website. This free service let's users set up one profile pic to rule them all. If a website know's your email address, it can pull the associated Gravatar using a pretty simple image link. The necessary HTML for your web application to use a Gravatar is:
< img src="http://www.gravatar.com/avatar/HASH/" />
You merely replace HASH with a MD5 hash of the user's email address and the magic is done.
Well, almost. Turns out getting an MD5 hash appears to require another step in .NET. I might have some basic lack of understanding about hashing, but my thought is that the code required to get an MD5 hash is much too complicated. Why this isn't just a built-in extension method on String is beyond me.
Instead the process involves using the System.Security.Cryptography.MD5 class, byte arrays, and a String Builder. Luckily I found a blog post that explained all this. You can find it and additional details on Gravatar images in the links below.