https://eauth.us.to/ - Your #1 Free and Powerful Software Licensing Solution, Ultimately providing you with the most secure features and easy to use on an authentication system.
Navigate to Eauth.cs, and fill these lines of code:
/* Required configuration */
private string accountKey = ""; // account key goes here
private string applicationKey = ""; // Your application key goes here
private string applicationID = ""; // Your application ID goes here
private string applicationVersion = "1.0"; // Your application version goes here