I have a silverlight application. I want the user to be able to logon using their windows credentials or better yet not have to logon at all, the application will just know who they are and approve them based on their user name.
Possible? If so then how?
Yes it is possible but not directly with Silverlight, you must use ASP.NET authentication for that.
Just create a separated webservice that is using Windows Integrated Authentication to get your data then the user validation will be on the server.
Heres two good article on how to do it :
http://msdn.microsoft.com/en-us/library/dd744835(v=vs.95).aspx
http://msdn.microsoft.com/en-us/magazine/ff646975.aspx