Connect C# app to a webpage

Hi, I'm new to web programming. I have a program written in C# (.Net Framework 4.0). I want it to get input from a single textBox located on a web page and I want to output some text to a multi-line textBox on that webpage. What's the easiest way to do that? What technologies do I need?

Google "c# web development tutorial". You will find many instructional sites dedicated to getting you started in C# development for the web.