Free eBook - OWASP Top 10 for .NET Developers
Go here, and download that eBook.
My one of the techie friend Troy Hunt (Microsoft MVP) got a free eBook titled "OWASP Top 10 for .NET developers" for you. I've gone through this eBook and find it awesome. He really did a great job. I recommend you to read this if you really want to improve your .NET security skills.
The complete eBook has 10 Parts with 255 Pages.