Page redirection in C#

Hello

 

When a new user successfully completes a 'Register' aspx form on a Web site, he sees another page that tells him "You have successfully registered" or, if not, he is directed back to the 'new user' registration form. 

 

How would I code that in C#, please, and would that code go in my current Register.aspx.cs file or inserted in another file (html, aspx.cs?) altogether? 

 

Thank you.