why hackers can decrypt my encrypted Connection String in web.config(C#)

My application is on the shared Hosting.I've encrypted my Connect开发者_如何学JAVAion String programmatically to make it secure. However, the hacker still is able to decrypt the encrpted Connection String adding scripts into the DB. Just wondering if there is a way to solve this problem? Many thanks !!!

.NET vulnerability discovered last September.

Make sure your .NET is up to date!

If the hacker gains control over your server, he can do anything your code can do. Can your code decrypt the Connection String? (apparently yes) Then he can do it, too.