Download CrypLib
CrypLib is a simple encoding library that you can use for your .net applications.
Written in c#.
Add reference in Visual Studio.
Add using statement to your app:
using CryptLib;

Call methods by passing string to encrypt or decrypt like:
string myKey = "MySecretKey";
string encryptedText = Crypt.Encrypt("NormalText",myKey);
string decryptedText = Crypt.Dencrypt("EfdDKLGwS8infg5c6ny+lTi6wEWAZ1ve+i+nToxWRLI=",myKey);
Encrypt connection strings in web.configs, settings files, etc.
Stack keys to make it even more difficult.